Nuclear Physics in Astrophysics XI

15 Sept 2024, 18:00 → 20 Sept 2024, 14:05 Europe/Berlin

Schönfeld-Hörsaal BAR/SCHÖ/E (TU Dresden, Germany; Barkhausen-Bau, Schönfeld-Hörsaal (BAR/SCHÖ/E))

Daniel Bemmerer (HZDR)

The Nuclear Physics in Astrophysics XI (NPA-XI) conference brings together scientists working in nuclear astrophysics, including laboratory experiments, theoretical nuclear physics, astronomy, and astrophysics.

 

NPA-XI is part of a series of conferences taking place every two years, under the auspices of the Nuclear Physics Division of the European Physical Society.

 

NPA-XI takes place from 15 - 20 September 2024 at TU Dresden, Germany. The conference was preceded by a scientific school, the NPA-XI school, in the week of 8-13 September.

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The NPA-XI conference acknowledges support from:

The conference is sponsored by:

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Circulars NPAXI_FinalCircular.pdf NPAXI_FirstCircular.pdf

Posters Poster_NPA_240820.pdf

Sunday 15 September

18:00 Registration

18:30 Welcome Reception

Monday 16 September

08:00 Registration

1 Opening and Welcome by HZDR, EPS, and EPJA

Speakers: Prof. Daniel Bemmerer (HZDR), Prof. Sebastian M. Schmidt (HZDR), Prof. Alessandra Fantoni (European Physical Society), Prof. David Blaschke (European Physical Journal A)

Plenary Session: A: Neutron capture processes (1). & The early Universe (1).

Convener: Eliana Masha (Helmholtz-Zentrum Dresden-Rossendorf e.V. (HZDR))

2 Finding metal-poor r-process stars to understand heavy element nucleosynthesis

Understanding the origin of the elements has been a decades-long pursuit, with many open questions remaining. Old stars found in the Milky Way and its dwarf satellite galaxies can provide answers because they preserve clean element abundance patterns of the nucleosynthesis processes that operated some 13 billion years ago, enabling reconstruction of the chemical evolution of the elements. This talk focuses on recent advances of finding r-process metal-poor stars and what their detailed abundance measurements can tell us about heavy element nucleosynthesis, actinide production and fission recycling.

Speaker: Prof. Anna Frebel (MIT)

3 The intermediate neutron capture process in AGB stars

Despite considerable progresses during the last decades, the origin of the elements heavier than iron is not yet fully understood. In addition to the slow (s) and rapid (r) neutron capture processes, an intermediate neutron capture process (i-process) is thought to exist at neutron densities intermediate between the s- and r-processes. The astrophysical site(s) hosting the i-process is (are) actively debated. After reviewing the current status of the i-process, I will focus on the development of the i-process in asymptotic giant branch (AGB) stellar models, computed with the stellar evolution code STAREVOL. I will highlight the unique chemical fingerprint of the i-process, identify key reaction rates and compare model predictions with observations of chemically peculiar stars.

Speaker: Arthur Choplin (Université Libre de Bruxelles)

slides_NPAXI_Choplin4.pdf

4 Stellar investigation at ultra iron-poor regime

The most iron-poor stars are thought to be among the oldest objects observable in the sky.
Understanding them provides us a deeper knowledge on formation and evolution of the pristine universe.
In fact, they are supposed to be formed from a gas enriched just by the explosion of the first generation of massive stars.
Their chemical inventory has the signature of the nucleosynthesis both during the life of the first-generation massive stars,
and in the supernovae explosion. It is then very sensitive to the masses of the first stellar generation.
Another key point is to detect binarity among these stars to understand how they formed.

The very few stars known with a really poor iron-content ([Fe/H]<-4.5) show diversity in their chemical content and peculiarities.
Some of them show variability in radial velocity, compatible with belonging to a multiple system.

With the aid of new observations, we investigated the binarity of some of these ultra Fe-poor stars, in particular the prototype ultra iron-poor star HE0107-5240 and other ultra Fe-poor stars.
We re-visited their chemical contents with particular attention to C isotopic ratio, sensitive to the nucleosynthesis of a possible more evolved candidate in the binary system during the asymptotic giant branch.

Speaker: Elisabetta Caffau (Observatoire de Paris)

147_Slides_Caffau.pdf

5 Nitrogen and Fluorine production in the early Universe

New rotating stellar models for the first generations of massive stars will be presented. Their results on nucleosynthesis will be compared with observed composition of very iron-poor stars and with the composition recently inferred by spectroscopy in high redshift galaxies by the JWST. We shall show that both fast-rotating Population III stars and/or non-rotating very massive stars up to 10,000 solar masses can reproduce the high N/O ratios observed in high redshift galaxies. We will also show the significant contribution of rotating very metal-poor stars on fluorine enrichment. Finally, we will discuss the impact of different implementations of the physics of rotation in stars, focusing on their impact on stellar nucleosynthesis.

Speaker: Sophie Tsiatsiou (University of Geneva)

SophieTsiatsiou.pdf

Poster Flashes: A

Every poster presenter has 1 minutes to present 1 slide summarizing the poster

6 Emulator for the r-process and its energy generation in neutron-star merger remnants

The rapid neutron-capture process ($r$-process), known to operate in neutron-star merger (NSM) remnants, produces heavy elements whose radioactive decay deposits energy into the ejecta and powers a distinctive thermal glow called kilonova. However, an online implementation of the $r$-process in simulations is challenging due to the associated large number of isotopes in a full nuclear network. In this talk, we will present a machine learning method to emulate the $r$-process and its energy generation that can be efficiently incorporated in hydrodynamic simulations. We use this method to study the effects of $r$-process heating on the properties of NSM ejecta and kilonova.

Speaker: Zewei Xiong (GSI Helmholtzzentrum für Schwerionenforschung)

poster_pitch_Xiong.pdf

7 Nuclear pasta in neutron stars

Theory has long predicted that a dense mantle consisting of exotic nuclear structures known as “nuclear pasta” exists between the crust and the core of a neutron star. Studying this possible phase of dense matter is important since its transport and mechanical properties differ markedly from those of the crust. Different types of pasta would thus leave an imprint on many observable aspects of neutron stars, from their magnetothermal evolution to the gravitational waves they emit. In this contribution, I study the emergence of pasta phases with parameterizations of a nuclear energy density functional that were accurately calibrated to both (I) thousands of experimental data points on nuclear structure and (ii) state-of-the-art ab initio predictions for dense matter. I will compare different levels of approximations: starting from a semi-classical approach in one dimension up to fully quantum-mechanical simulations in three dimensions. In particular, I will show how the inclusion of quantum effects in the modeling impacts the formation of nuclear pasta.

[1] N. N. Shchechilin, N. Chamel, J. M. Pearson, Physical Review C, 108, 025805 (2023)

Speaker: Nikolai Shchechilin (Universite Libre de Bruxelles)

Slide_dresden24.pdf

8 A novel numerical library for neutrino-matter interaction rates in binary neutron star mergers

GW170817 marked the first outstanding detection of a gravitational-wave signal generated by the coalescence of a binary neutron star (BNS) system. The successful follow-up campaign carried out by electromagnetic facilities has confirmed the remarkable scientific potential of such events in the context of newborn multimessenger astrophysics. In this respect, reliable theoretical modeling of the coalescence is crucial to avoid systematic errors when interpreting observations. Among the important physical effects to be considered, the interplay between neutrinos and nuclear matter can generate distinct fingerprints on the coalescence, such as affecting the stability of the remnant in the merger aftermath or defining the initial conditions from which the rapid neutron capture process in the ejecta takes on.

To this end, we present “bns_nurates”, a novel numerical library written to compute neutrino-matter interaction rates in BNS context. “bns_nurates” is designed to account for different kinds of nuclear physics effects on the interaction rates. As an example of application, we compare the importance of different reaction rates for typical conditions realized during the post-merger phase. Such a study can help to select which relevant reactions need to be included to correctly predict the impact of neutrinos on the system.

Speaker: Leonardo Chiesa (University of Trento)

NPA_XI_poster_pitch_slide_Leonardo_Chiesa_#32.pdf

9 CERES survey: chemical abundances of neutron capture elements up to Eu

The rapid neutron capture process is responsible for the synthesis of roughly half of the elements heavier than Zn ($Z>30$) in the solar system, however, it is still unclear what the exact astrophysical sites of the r-process are, and if different r-process nucleosynthetic channels exist, particularly at low metallicities. Metal-poor stars play a key role in understanding the nucleosynthesis of heavy elements in the early Universe, as their chemical abundances reflects the composition of the gas in which they formed. These stars show a variety of heavy chemical abundances patterns, with extreme variation in the r-process elements, from $[\mathrm{Eu}/\mathrm{Fe}]$ below solar to $[\mathrm{Eu}/\mathrm{Fe}]>1$ in r-rich stars. This large scatter in heavy elements abundances seems to suggest that more than one formation site is responsible for the nucleosynthesis of these elements, and that the formation happens under different physical conditions.

In this talk I will present the new abundance results of heavy neutron capture elements, including the poorly studied Ru and Ag, for a sample of 52 very metal-poor stars ($[\mathrm{Fe}/\mathrm{H}]<-1.5$). The talk will be focused on exploring the impact of the r-process at low metallicities, by comparing the observed chemical abundances with those predicted by theoretical models.

Speaker: Linda Lombardo (Goethe University Frankfurt)

one-slide_llombardo_id35.pdf

10 The SHADES Project: Underground Measurement of the Low Energy ${}^{22}$Ne($\alpha$,n)${}^{25}$Mg Cross Section

Synthesis of neutron-rich isotopes is widely considered to occur via the slow neutron-capture processes (weak and main s-process). The reactions ${}^{13}\mathrm{C}(\alpha,\mathrm{n}){}^{16}\mathrm{O}$ and ${}^{22}\mathrm{Ne}(\alpha,\mathrm{n}){}^{25}\mathrm{Mg}$ are the main neutron sources for this process; the LUNA collaboration has measured the former reaction to high precision at energies relevant for AGB stars ($>90\,\mathrm{MK}$). However, the latter reaction remains experimentally unconstrained at the astrophysically relevant temperatures for helium shell burning, $0.2–0.3\,\mathrm{GK}$, or centre-of-mass energies $450–750\,\mathrm{keV}$. In particular, the state-of-art reaction rate is represented only by an upper limit at energies below $680\,\mathrm{keV}$. To address this knowledge gap, a recent campaign is ongoing using the LUNA-MV accelerator to directly measure the ${}^{22}\mathrm{Ne}(\alpha,\mathrm{n}){}^{25}\mathrm{Mg}$ cross section in the astrophysical energy range. This experiment will exploit the new neutron counter array SHADES installed downstream from a ${}^{22}\mathrm{Ne}$ gas target. Thanks to the very low natural neutron background at the Laboratori Nazionali del Gran Sasso and the innovative SHADES array, the rate is envisioned to have an improved sensitivity of $> 2$ orders of magnitude over previous measurements. This poster will present an overview of the SHADES array along with preliminary results collected at and above the important $704\,\mathrm{keV}$ resonance using the LUNA-MV accelerator.

Speaker: Thomas Chillery (Laboratori Nazionali del Gran Sasso)

036_221_Pitch.pdf

11 The New Deep-underground Direct Measurement of ${}^{22}\mathrm{Ne}(\alpha,\gamma){}^{26}\mathrm{Mg}$ with EAS$\gamma$: a feasibility study

The reaction ${}^{22}\mathrm{Ne}(\alpha,\gamma){}^{26}\mathrm{Mg}$ is associated with several questions in nuclear astrophysics, such as the Mg isotope ratio in stellar atmospheres and the nucleosynthesis of elements beyond Fe through its competition with the neutron source ${}^{22}\mathrm{Ne}(\alpha,n){}^{25}\mathrm{Mg}$.

Due to the low stellar energies and therefore very low cross section, direct experiments have been only able to provide upper limits below a strong resonance at $832\,\mathrm{keV}$.

The purpose of the EAS$\gamma$ project is to perform the first direct measurement of the ${}^{22}\mathrm{Ne}(\alpha,\gamma){}^{26}\mathrm{Mg}$ in the range of astrophysical interest below $600-800\,\mathrm{keV}$ and the remeasurement of the important $832\,\mathrm{keV}$ resonance.

The measurement will be performed at Laboratori Nazionali del Gran Sasso and will be carried out using a high $\alpha$ particle current delivered by the newly commissioned LUNA MV accelerator.

Moreover, its position underground and additional passive shielding will reduce the $\gamma$-background, drastically increasing the sensitivity over the state of the art. The $\gamma$-rays produced in the reaction will be detected by a NaI scintillator array surrounding a windowless, recirculating gas target.

I will present the current status of the project and the preliminary results of NaI detector array simulation and characterisation.

Speaker: Daniela Mercogliano (INFN-Na and Unina)

ID37_Mercogliano_PosterPitch.pdf

ID37_poster.pdf

12 Complete r-Process Survey

The production of heavy elements by the rapid neutron capture process (r-process) can occur in neutron star mergers and probably in supernovae driven by strong magnetic fields. We use a complementary method to using trajectories from simulations and explore a complete and extended range of astrophysical conditions with a parametric model. This allows us to investigate all possible conditions for the r-process, also beyond current simulations. Final abundances are in good agreement with those of Lagrangian tracer particles from simulations. Therefore, our survey can be used to compare to observations and investigate the impact of the nuclear physics input.

Speaker: Jan Kuske (TU Darmstadt)

JanKuskeNPAFlashTalk.pdf

13 Experimental study of the ${}^{29}$Si(p,$\gamma$)${}^{30}$P reaction for classical nova nucleosynthesis

$^{29}$Si is believed to be produced during classical nova events. The measurements of the isotopic ratios in primitive meteorites can represent precisely the amount of $^{29}$Si produced by such events. However, there is no unambiguous evidence for the nova paternity of presolar stardust grains. Therefore, it is important to know precisely how much $^{29}$Si is produced in classical novae.

To do reliable theoretical calculations, we need to know the cross section of the $^{29}\mathrm{Si}(\mathrm{p},\gamma)^{30}\mathrm{P}$ reaction at astrophysically relevant energies. The direct capture (DC) cross section of $^{29}\mathrm{Si}(\mathrm{p},\gamma)^{30}\mathrm{P}$ has not been measured so far and for the strengths of some low energy resonances ambiguous data can be found in the literature. Therefore, the aim of the present work was the experimental study of this reaction. The strength of the $E_\mathrm{p}=416\,\mathrm{keV}$ resonance was measured as well as the DC cross section. For the measurements the proton beam was provided by the Tandetron accelerator of Atomki. The natural abundance of $^{29}$Si is about $4\%$, so enriched targets are necessary for the DC experiments. For resonance strength natural isotopic composition SiO$_{2}$ thick targets were used.

In this poster I present the details of the experimental procedure and some results.

Speaker: Zsolt Mátyus (HUN-REN Institute for Nuclear Research)

posterflash_Zs_Matyus.pdf

14 Nucleosynthesis and Kilonova in Neutron Star Mergers: Impact of Nuclear Matter Properties

Matter expelled from binary neutron star (BNS) mergers can harbor r-process nucleosynthesis and power a Kilonova (KN). Both the elemental yields and the KN transient are intimately related to the astrophysical conditions of the merger ejecta, which in turn indirectly depend on the equation of state (EOS) describing the nuclear matter inside the NS. In particular, the merger evolution is influenced by the nuclear matter properties that characterize the EOS around and above nuclear saturation density.

We consider the outcome of a set of BNS merger simulations employing different finite-temperature nuclear EOSs, obtained from Skyrme-type interaction models. We study the ejecta using a nuclear reaction network coupled with a semi-analytic KN model.

The final elemental abundances and the associated KN light curves are found to be non-trivially influenced by the nuclear matter properties used to parametrize the EOS, specifically the incompressibility and the nucleon effective mass at saturation density. A major role is played by the overall amount of each ejecta component, highlighting the strong degeneracy that intervenes between the merger outcome and the behaviour of the intrinsic nuclear matter.

Speaker: Giacomo Ricigliano (Technical University of Darmstadt)

Flash NPAXI.pdf

15 Low energy measurement of the ${}^{96}$Zr($\alpha$,n)${}^{99}$Mo, ${}^{100}$Mo($\alpha$,n)${}^{103}$Ru and ${}^{86}$Kr($\alpha$,n)${}^{89}$Sr reactions for studying the weak r-process nucleosynthesis

The light ($30 < Z < 45$) neutron-rich isotopes are thought to be synthesized in the neutrino-driven ejecta of core-collapse supernova via the weak r-process [1]. Recent nucleosynthesis studies have shown that $(\alpha,n)$ reactions play an important role in their production. The rates of these reactions have been calculated using statistical models, and their main uncertainty at the energies relevant to the weak r-process comes from the $\alpha+\mathrm{nucleus}$ optical potential. Several sets of parameters are available for the calculation of the $\alpha+\mathrm{nucleus}$ optical potential, leading to large deviations of reaction rates, exceeding even one order of magnitude.

To constrain the parameters of the $\alpha+\mathrm{nucleus}$ optical potential and to provide high precision reaction rates for astrophysical simulations, recently the cross sections of the $^{96}\mathrm{Zr}(\alpha,\mathrm{n}){}^{99}\mathrm{Mo}$, ${}^{100}\mathrm{Mo}(\alpha,\mathrm{n}){}^{103}\mathrm{Ru}$ and ${}^{86}\mathrm{Kr}(\alpha,\mathrm{n}){}^{89}\mathrm{Sr}$ reactions were measured at the Gamow-window for the first time [2,3]. Details on the experimental approach, on the new ATOMKI-V2 potential [4] will be presented and an outlook into the astrophysical application of the data will be provided.

[1] A. Arcones and F. Montes, Astrophys. J. 731 5 (2011).
[2] G.G. Kiss et al., Astrophys. J. 908 202 (2021).
[3] T.N. Szegedi et al., PRC 104 035804 (2021).
[4] P. Mohr et al., PRL 124 252701 (2020).

Speaker: Sándor Kovács (HUN-REN Institute for Nuclear Research)

SRK_FlashTalk_id46.pdf

16 Constraining the ${}^{69}$Zn Neutron Capture Cross-Section via the Beta-Oslo Method

The existence of the weak intermediate neutron-capture process (i-process) explains the observed astrophysical abundances of elements around the $Z<50$ region. Neutron capture reactions in the $A=70$ mass region for Ni, Cu, and Zn isotopes are known to produce large variations in predicted i-process abundances. Predicted stellar abundances of Ga are particularly affected by the $^{69}\mathrm{Zn}(\mathrm{n},\gamma){}^{70}\mathrm{Zn}$ reaction. The $\beta$-decay of ${}^{70}\mathrm{Cu}$ offers an unique opportunity to utilize the $\beta$-Oslo method to experimentally determine the $\gamma$-ray strength function and nuclear level density and constrain the ${}^{69}\mathrm{Zn}(\mathrm{n},\gamma){}^{70}\mathrm{Zn}$ reaction rate for i-process nucleosynthesis. ${}^{70}\mathrm{Cu}$ has three different $\beta$-decaying spin-parity states that populate different spin ranges at similar excitation energies in the daughter nucleus: the $6^-$ ground state, the $101\,\mathrm{keV}$ $3^-$ isomeric state, and the $242\,\mathrm{keV}$ $1^+$ isomeric state. In experiments performed at the NSCL and FRIB, the isomers and ground state of $^{70}\mathrm{Cu}$ were produced and delivered to the Low Energy Beam and Ion Trap (LEBIT) and then to Summing NaI (SuN) Total Absorption Spectrometer. Preliminary results from $\beta$-Oslo analysis will be presented along with the preliminary constrained ${}^{69}\mathrm{Zn}(\mathrm{n},\gamma){}^{70}\mathrm{Zn}$ cross-section. Initial results from the commissioning of the SuN upgrade (to SuN++) will also be presented.

Speaker: Eleanor Ronning (Michigan State University/FRIB)

Ronning_NPA_2024.pdf

Ronning_NPA_Poster_Pitch_2024.pdf

17 Core-collapse supernova yields in galactic chemical evolution

The amount and composition of matter ejected in core-collapse supernovae (CCSNe) are key uncertainties in models of galactic chemical evolution (GCE). Extensive grids of stellar models with varying mass and metallicity are needed. Although 3D simulations of stellar evolution and CCSNe have recently become available, the large computational cost only allows large sets of simulations under the assumption of spherical symmetry. In this study, we simulate the collapse and explosion of 67 massive stars with zero-age main sequence masses between 11 and 75 solar masses and three different metallicities. Our CCSN simulations include a self-consistent treatment of the proto-neutron star with a naturally evolving mass cut between remnant and ejecta. We provide nucleosynthesis results from an in-situ nuclear reaction network and use them as input for a GCE model of the Milky Way. This self-consistent chain allows for the exploration of uncertainties and comparison of the results to observations. With this study, we want to encourage the communities of stellar evolution and supernova simulations to use the latest advances in the respective fields to provide information useful for GCE models.

Speaker: Finia Jost (Technical University Darmstadt)

055_231_Pitch.pdf

18 Measurement of neutron capture cross section of $^{30}$Si at n_TOF

Neutron capture cross sections of $^{30}$Si are an important parameter to study the origin of silicon in our Solar System and understand isotopic abundances in SiC presolar grains. The bulk of $^{30}$Si present in our Galaxy is produced in massive stars during carbon shell burning phases and its neutron capture cross sections strongly impact on its abundance. An accurate value of the neutron capture cross section of $^{30}$Si is also needed to disentangle the contributions of the s-process nucleosynthesis to the silicon abundances measured in mainstream SiC grains in order to test stellar evolution models. Since available experimental data are scarce and discrepant (the two most recent measurements show a discrepancy in the stellar cross section of approximately a factor 2), a new accurate time-of-flight measurement was carried out during summer 2023 at the n_TOF facility at CERN. The preliminary results show important discrepancies with respect to cross sections recommended in nuclear data libraries: only one resonance at 4.98 keV is observed compared to the two resonances expected below 100 keV and an additional resonance at approximately 15.14 keV is observed. In this contribution, the motivation, the measurement and these preliminary results will be presented.

Speaker: Michele Spelta (University of Trieste & INFN - Sez. di Trieste)

Poster_Pitch_NPAXI_Si30_id86.pdf

19 Measurement of neutron capture cross section of $^{64}$Ni at n_TOF

Neutron capture cross sections of $^{64}$Ni is an important parameter to accurately simulate the s-process and validate stellar models. As $^{64}$Ni is among the seeds of the s-process, the uncertainty on its capture cross section has been shown to significantly affect the predicted abundances of many isotopes produced by the s-process both in massive and AGB stars. Moreover, the uncertain value of this cross section may be the cause of the discrepancy observed between predicted and measured $^{64}$Ni isotopic ratios in SiC presolar grains. Indeed, the MACS reported by different releases of data libraries show discrepancies higher than a factor 2 at 5 keV. For these reasons, a new accurate time-of-flight measurement was carried out during summer 2023 at the n_TOF facility at CERN. The preliminary results confirm most of the resonances up to 100 keV, except for a huge resonance at 9.52 keV, reported in many of the most recent data library releases. As this resonance was expected to contribute more than 60% to the MACS at 5 keV, a significant reduction of the value reported in the most recent library releases is expected. Motivation, measurement and these preliminary results will be presented.

Speaker: Michele Spelta (University of Trieste & INFN - Sez. di Trieste)

Poster_Pitch_NPAXI_Ni64_id87.pdf

20 Using slow ions in accelerator mass spectrometry for experimental nuclear astrophysics

Accelerator Mass Spectrometry (AMS) is the most sensitive technique for direct atom counting of many long-lived radionuclides. The addition of a buffer gas-filled ion cooler to the low-energy side of the AMS system opens up exciting new possibilities, especially in the mass range $60-200\,\mathrm{amu}$. The new ion cooler ILTIS, built at Helmholtz-Zentrum Dresden-Rossendorf in cooperation with the University of Vienna will be added to the new dedicated $1\,\mathrm{MV}$ AMS facility HAMSTER in Dresden. In the ion cooler, the near-thermal ion beam is collinearly overlapped with a laser beam to induce laser photodetachment ($A^– + \gamma \to A + e^-$). Using suitable molecules, this neutralizes any interfering atomic isobar while leaving the isotope of interest unaffected. Some radionuclides, whose detection has already been proven to benefit from this technique are e.g. ${}^{26}\mathrm{Al}$, ${}^{36}\mathrm{Cl}$, ${}^{90}\mathrm{Sr}$, ${}^{135}\mathrm{Cs}$ and ${}^{182}\mathrm{Hf}$. We will highlight the new measurement capabilities of ILTIS and give an outlook on AMS measurements of ${}^{90}\mathrm{Sr}$ and ${}^{135}\mathrm{Cs}$. AMS can provide direct assessments of the thermal and epithermal neutron capture cross sections on the radioactive target nuclei ${}^{134}\mathrm{Cs}$ and ${}^{89}\mathrm{Sr}$, leading to ${}^{135}\mathrm{Cs}$ ($T_{1/2} = 2.3\,\mathrm{Myr}$) and ${}^{90}\mathrm{Sr}$ ($28.91\,\mathrm{yr}$), respectively, which can serve as an anchor point for estimating the important cross sections in the astrophysical relevant keV-energy region.

Speaker: Alexander Wieser (Helmholtz-Zentrum Dresden-Rossendorf - Accelerator Mass Spectrometry and Isotope Research)

pitch.pdf

11:05 Coffee Break

Plenary Session: B: Neutron capture processes (2). & Neutron stars (1).

Convener: Dr Cristina Chiappini (Karte von Leibniz-Institut für Astrophysik Potsdam Leibniz-Institut für Astrophysik Potsdam)

21 Neutron-capture measurements for s-process nucleosynthesis

There are three “families” of nuclides with a particular value for s-process studies: s-only nuclei, bottlenecks and branchings. Interestingly, for none of them is the situation satisfactory from an experimental standpoint.
This contribution summarizes selected examples utilizing the time-of-flight technique at CERN n_TOF in combination with detection systems, which have been progressively optimized over the last 25 years. Also, new endeavors combining radioactive-ion beams from ISOLDE with a new cyclic activation station (CYCLING) at CERN n_TOF NEAR will be introduced as a means to tackle some specific s-branching nuclei. Some of the latest experimental advances in the field will be presented, together with their astrophysical impact on branching points (79Se, 94Nb), branchings leading to s-only nuclei (like 204Tl-204Pb) and very-low capture cross-section nuclei or bottlenecks (140Ce, 209Bi). On the basis of these new exciting results, also current limitations on state-of-the-art techniques will be depicted, thereby showing the pressing need for further upgrades and enhancements on both facilities and detectors. Finally, it will be discussed how the combination of conventional methods, TOF and activation, with complementary novel approaches based on inverse-kinematics experiments, may allow one to go one step ahead toward completing the large puzzle of the s-process data needs.

Speaker: Cesar Domingo Pardo (IFIC (CSIC - University of Valencia))

npaxi_CesarDomingo_upload.pdf

22 Latest news and future prospects on measurements of neutron star masses and radii

More than 50 years after the discovery of neutrons stars, their interior composition and structure remain unknown. Because the extreme densities and matter asymmetry in neutron star interiors are out of reach for Earth laboratories, the equation of state of bulk nuclear matter is unknown, and its determination would have implication for astrophysics and nuclear physics. Thankfully, measurements of neutron stars masses and radii are direct probes of the interior of these compact objects, and therefore on the composition and behaviour of dense nuclear matter. Mass measurements have been accessible from radio pulsars in binary systems since the discovery of the Hulse-Taylor pulsar in the 1970s, providing exquisite precisions for neutron stars between $1.2$ and about $2.1$ solar masses. In the past two decades, X-ray observatories have provided some measurements of neutron star radii, but with limited precision in comparison to the mass measurements. However, recently, the results from the NICER Observatory showed the most promising, robust and precise measurements. I will give a quick historical overview of mass and radius measurements, followed by a presentation of the key and recent results from the NICER mission. The talk will finish with a discussion of expected constraints from future observatories.

Speaker: Sebastien Guillot (IRAP / CNRS)

Guillot NPA-XI 2024.pdf

Guillot NPA-XI 2024.pptx

23 Nucleosynthesis of $^{60}$Fe via indirect neutron-capture reaction studies

Active nucleosynthesis in our galaxy can be observed directly through the detection of long-lived radioactivities. Isotopes such as $^{26}$Al, and $^{60}$Fe have been observed either in solar system samples or through $\gamma$-ray observations within the galaxy. Both isotopes are predominantly produced in massive stars and ejected into the interstellar medium either via stellar winds or through the supernova explosion. Instead of only looking at absolute observational values for each isotope, the ratio of $^{60}$Fe/$^{26}$Al can be used as a more sensitive probe of massive star evolution since many of the observational uncertainties cancel out. A long standing puzzle is that most theoretical models over-predict this ratio compared to observations. The discrepancy has been attributed to uncertainties in the nuclear reactions, and in particular the ones related to the production/destruction of $^{60}$Fe. Here we report on the main reaction producing $^{60}$Fe, namely the $^{59}\mathrm{Fe}(n,\gamma){}^{60}\mathrm{Fe}$ reaction. We will present the results of a $\beta$-Oslo measurement that provides an indirect experimental constraint for this reaction. The impact of this result on the evolution and explosion of massive stars will be presented.

Speaker: Artemis Spyrou (Michigan State University)

Spyrou_NPA2024.pdf

Spyrou_NPA2024.pptx

Poster Flashes: B

Every poster presenter has 1 minutes to present 1 slide summarizing the poster

24 Repairing $^{205}$Pb as an early Solar System chronometer by measuring the bound-state beta decay of $^{205}$Tl

Lead-205 looks like a promising cosmochronometer for the early Solar System due to its unique position among astrophysically short-lived radionuclides as an s-only isotope probing the termination of the s process [1]. Unfortunately, the 2.3 keV first excited state in $^{205}$Pb reduces the half-life in stellar environments by around 6 orders of magnitude, which could severely inhibit $^{205}$Pb production. However, Yokoi et. al. [2] pointed out that the bound-state $\beta$ decay of $^{205}$Tl could counter-balance this decay by producing $^{205}$Pb. To clarify the complex production of $^{205}$Pb, we measured the bound-state $\beta$ decay of $^{205}$Tl$^{81+}$ at the Experimental Storage Ring in GSI, Darmstadt. From the measured half-life, we calculated new weak decay rates for a wide range of astrophysical conditions. AGB stellar nucleosynthesis models based on these new rates saw approximately a factor 2 increase in $^{205}$Pb production (when legacy rates were controlled). With new production ratios, we predicted an updated steady-state interstellar medium (ISM) $^{205}$Pb/$^{204}$Pb ratio. By comparing the ISM ratio to the ratio measured in the earliest meteorites, we derived, for the first time, a positive time interval for the isolation period of the solar material from enrichment.
[1] Lugaro (2018) PPNP 102:1–47.
[2] Yokoi (1985) A&A 145:339–346.

Speaker: Dr Iris Dillmann (TRIUMF)

205Pb_ESS-NPA-XI_1min_pitch.pdf

205Pb_ESS-NPA-XI_poster.pdf

25 Weak rates determining the production of the $^{205}$Pb cosmochronometer in AGB stars

$^{205}$Pb has been proposed as a cosmochronometer for the early solar system as it is only produced in the s-process and has a half-life of 17 My. This half-life can change dramatically in the stellar environment depending on the ionization stage of $^{205}$Pb and $^{205}$Tl and the thermal population of excited nuclear states. $^{205}$Pb has an excited 1/2$^-$ state at 2.3 keV that shortens its half-life by six orders of magnitude. On the other hand $^{205}$Pb can be produced by bound-state beta decay of highly ionized $^{205}$Tl. To reliably model the synthesis of $^{205}$Pb in AGB stars therefore requires a consistent treatment of both electron capture rates in $^{205}$Pb and bound-state beta decay rates in $^{205}$Tl for a wide range of temperatures and densities. Compared to previous work by Takahashi and Yokoi we could improve the rates by using an experimentally determined value for the bound-state beta decay of $^{205}$Tl that has been measured recently by the E121 collaboration at GSI. We also improved the description of the interaction between ions and plasma and used Dirac-Hartee-Fock calculations for the spectra and wave functions of the $^{205}$Pb and $^{205}$Tl ions.

Supported by the Deutsche Forschungsgemeinschaft – Project-ID 279384907 – SFB 1245.

Speaker: Thomas Neff (GSI Helmholtzzentrum für Schwerionenforschung, Germany)

NPA-Poster-Neff-88.pdf

NPA-PosterPitch-Neff-88.pdf

26 Bayesian study of quasi-universal relations for neutron stars normal modes

Gravitational wave asteroseismology is a promising approach for studying neutron stars' characteristics and constraining dense matter equation of state (EoS).  Several quasi-universal empirical relations have been developed to link the frequencies of normal modes to various stellar properties such as mass and radius. These relations allow us to extract macroscopic information about the stars from a detected signal. However, their universality is typically tested using a small number of distinct nuclear models.

We use Bayesian inference employing the so-called meta-modeling technique to investigate a large set of equations of state that are compatible with astrophysical constraints, nuclear-physics experimental data, and current theoretical estimates from chiral effective field theory. To this aim, we employ a Markov chain Monte Carlo algorithm for the sampling of the posterior with high statistics. The modes are, then, evaluated using the Cowling approximations for all the equations of state making possible to test the universality for a large set of EoS compatible with the aforementioned constraints.

Speaker: Gabriele Montefusco (CNRS)

Poster.pdf

Poster_pitch.pdf

27 Alpha induced reactions on $^{124}$Xe for the astrophysical p-process

Majority of the heavy chemical elements are formed via neutron capture reactions. However, there are a few proton rich nuclei (p-isotopes) which cannot be created these ways.In a high temperature environment pre-existing nuclei can photodissociate, and through $(\gamma,\mathrm{n})$ reactions the p-isotopes can be created. Subsequent $(\gamma,\mathrm{n})$ reactions increase the neutron separation energy, and charged particle release in $(\gamma,\alpha)$ and $(\gamma,\mathrm{p})$ reactions become favourable, diverting the reaction flow towards lower masses.

Reaction network calculations using astrophysical and nuclear input parameters often fail to reproduce the abundances of naturally occurring p-isotopes. The input reaction rates are usually derived from the Hauser-Feshbach statistical model with considerable uncertainty. Benchmarking the model calculation is crucial for accurate predictions. Experimentally the cross section of the radiative capture is determined, and the photodisintegration rate is derived employing the detailed balance.

In this study, the cross section of $^{124}\mathrm{Xe}(\alpha,\gamma){}^{128}\mathrm{Ba}$ and ${}^{124}\mathrm{Xe}(\alpha,\mathrm{n}){}^{127}\mathrm{Ba}$ was measured by the activation technique using Atomki's cyclotron accelerator. The experiments were performed using a thin-window gas cell in the astrophysically relevant energy range $E_\alpha = 10-15 \,\mathrm{MeV}$. The $\gamma$-photons following the decay of the reaction products were detected with a high purity germanium detector.

Details of the experiment and preliminary results will be presented.

Speaker: Ákos Tóth (HUN-REN ATOMKI)

poster_AT_ID67.pdf

poster_flash_AT.pdf

28 Late time behaviour of the kilonova light curves

Among the different signals in multimessenger astrophysics, the kilonovae are of particular interest to nuclear physicists. These electromagnetic signals can emerge from the ejecta of neutron star (NS) - NS mergers [1]. They are expected to be powered by nuclear decays since such mergers are considered dominant sites for r-process nucleosynthesis of heavy (unstable) nuclei. Even though there exist several works based on r-process network calculations, there remain loopholes in our understanding of the energy production in kilonovae. It is not easy to pin down the interplay between nuclear physics and astrophysics and new findings still emerge [2].

In this talk, we shall revisit one of the earliest kilonova models by Li and Paczynski [3] with some improvements and present a detailed analysis using all available data on the different nuclear decay modes. We shall point out some interesting features of the competition between the different decay modes at different time scales and present some hitherto unnoticed features of their role in the luminosity curves at late times.

[1] M. R. Drout et al. Science 358, 1570 (2017).
[2] Yu-Han Yang et al., Nature 626, 742 (2024).
[3] Li-Xin Li and B. Paczynski, The Astrophys. J. 507, L59 (1998).

Speaker: Dr Diego Ferney Rojas-Gamboa (Universidad de los Andes, Bogota, Colombia)

070_238_Pitch.pdf

29 Incorporating thermal effects into alpha decay half-life calculations for nucleosynthesis investigations

Theoretical models aiming to accurately reproduce observed nuclear abundances require complex calculations utilizing nuclear reaction networks. These networks encompass the nature of nuclear reactions and decays, accounting for both the production and destruction of nuclei. The explosive conditions in r-process sites, where temperatures rise to the order of Giga Kelvin, may lead to nuclei existing in excited states. While the effects of nuclear thermal excitations are typically considered in processes like neutron capture and photon disintegration, a similar treatment is often overlooked in the case of alpha decay. Instead, information regarding decay modes is typically derived from measurements conducted on Earth, where nuclei predominantly reside in their ground state. However, it is crucial to account for the temperature dependence of nuclear decay rates of alpha emitters. The standard formulation is achieved by summing over the half-lives of excited states of a nucleus for a specific type of decay. To facilitate a comprehensive investigation into the role of alpha decay half-lives of thermally excited nuclei in nucleosynthesis calculations, we propose an empirical formula. This formula, derived from a model for the alpha decay half-lives of excited nuclei via fitting available data, will serve to incorporate temperature-dependent half-life calculations into nucleosynthesis models.

Speaker: Diego Ferney Rojas Gamboa (Universidad de los Andes)

Poster_NPA-XI_DIEGOROJAS.pdf

Poster_pitch_DIEGOROJAS.pdf

30 Contribution of individual astrophysical events to chemical evolution of dwarf galaxies

Stars of different properties produce different elements. For instance, rotating massive stars are supposed to produce trans-iron elements at low metallicities (e.g. Frischknecht et al. 2012, Limongi & Chieffi 2018). Also, in low-mass galaxies, astrophysical events can appear sporadically. Thus, the relative contribution of astrophysical events to the chemical enrichment may not be compared to that in the solar neighbourhood.

Dwarf galaxies provide insights into the chemical enrichment in low-mass and low-metallicity systems. According to the cosmological model, massive galaxies are formed through mergers of less massive galaxies. When a dwarf galaxy is formed from lower-mass galaxies, individual events influence abundances ratios of each building-block galaxy, and the impact may be reflected in the ratios of the merged galaxy.

We investigate the contribution of individual events to the chemical enrichment of a dwarf galaxy in a context of hierarchical galaxy formation. The chemical evolution of building-block galaxies is derived with a numerical model where the stochasticity is introduced into the occurrence of astrophysical events. We discuss that the contribution of r-process events to the chemical enrichment may be large at low metallicities and that rotating massive stars can create part of the dispersion in abundance ratios through the weak s-process.

Speaker: Nao Fukagawa (National Astronomical Observatory of Japan)

one-minute-pitch_NPA-XI_71_NFukagawa.pdf

31 What is the Final Fate of Intermediate Mass Stars: Thermonuclear or Core-Collapse Supernova?

The fate of stars with intermediate mass ($\approx 7-11 \, M_\odot$) is still not certain. In their final stages, they develop degenerate oxygen-neon cores, potentially culminating in electron capture supernovae. Both a thermonuclear explosion, as well as a collapse to a neutron star are possible, critically depending on the oxygen ignition density. Understanding the oxygen ignition process is crucial to draw further conclusions and 3D hydrodynamical simulations are needed. In the late stages of evolution, forbidden electron captures, like the second forbidden transition between the ground states of ${}^{20}\mathrm{Ne}$ and ${}^{20}\mathrm{F}$, play a key role and significantly influence the density profile at the time of oxygen ignition. In addition, heating due to electron capture processes on ${}^{24}\mathrm{Mg}$ and ${}^{24}\mathrm{Na}$ leads to convectively unstable regions, which may not be correctly described in 1D stellar evolution codes like MESA. We aim to evaluate the impact of these convectively unstable regions and their impact on the later ignition of oxygen burning by employing the 3D hydrodynamical Seven-League Hydro code, while also considering the relevant electron capture rates.

Work supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) Project-ID MA 4248/3-1; RO 3676/7-1.

Speaker: Paul Christians (GSI Helmholtzzentrum für Schwerionenforschung)

Poster_Pitch_75.pdf

32 Experimental cross section of the $^3$He($\alpha$,$\gamma$)$^7$Be reaction around $E_\mathrm{cm}=3\,\mathrm{MeV}$

The ${}^3\mathrm{He}(\alpha,\gamma){}^7\mathrm{Be}$ reaction plays a major role both in the big bang nucleosynthesis (BBN) where it affects the primordial $^7$Li production, and in the solar energy generation via the pp-chain where as a branching point it affects the flux of neutrinos. Precise understanding of the reaction mechanism is of crucial importance for BBN and solar model calculations.

In case of the energy range relevant in the BBN, there are few experimental datasets, however in the solar relevant energy range it is impossible to measure experimental cross sections. For the solar models, one has to rely on extrapolation from higher energy datasets.
To aid these extrapolations, in the present study the reaction cross section was measured in the energy range covered so far with only one experimental dataset. The well known activation technique was employed, using a thin-window gas cell target containing $^3$He gas. The irradiations were performed by the cyclotron accelerator of Atomki. The $\gamma$-photons following the decay of the reaction products were detected with high purity germanium detector.

Details of the experiment and preliminary results will be presented along with a literature overview of the reaction and future plans to pinpoint crucial unknowns regarding this important reaction.

Speaker: Dr Tamás Szücs (Institute for Nuclear Research (Atomki))

#77_tszucs_3He_ag.pdf

33 Half-life and β-delayed neutron measurements of neutron-rich nuclei near N=126 at RIBF

The neutron-rich $N\sim126$ region is important to r-process calculations and has been less explored by experiments. This region is unique for its strong competition between allowed and first-forbidden transitions [1], which complicates half-life predictions. Besides, the position of the third r-process abundance peak and production of actinides are sensitive to half-lives of $N=126$ isotones [2,3]. Measurements of more exotic nuclei are essential to verify theoretical models commonly used in r-process calculations.

We will present results from the BRIKEN experiment [4] at RIBF. Particle identification was confirmed by the BigRIPS separator and a silicon energy-loss telescope. On the first attempt by RIBF, half-lives and beta-delayed neutron-emission probabilities ($P_n$) of $N\sim126$ exotic isotopes—some never been measured before—were determined by the WAS3ABi beta-counting system [5] and the BRIKEN neutron counter [6]. Preliminary results of $Z\leq79$ isotopes will be discussed.

References
[1] Zs. Podolyák, EPJ Web of Conf. 260, 03005 (2022).
[2] T. Suzuki et al., Astrophys. J. 859(2), 133 (2018).
[3] E. Holmbeck et al., Astrophys. J. 870(1), 23 (2018).
[4] T. T. Yeung et al., arXiv:2401.06428 (2024). https://arxiv.org/abs/2401.06428
[5] S. Nishimura, Prog. Theor. Exp. Phys. 2012(1), 03C006 (2012).
[6] A. Tolosa-Delgado et al., Nucl. Instrum. Methods. Phys. Res. A 925-133 (2019).

Speaker: Tik Tsun Yeung (The University of Tokyo)

NPA-XI pitch_Yeung.pdf

34 Shedding light on the brightest supernovae

Superluminous supernovae are a class of exceedingly bright transients whose luminosity cannot be comfortably explained by the standard 56Ni-decay picture. The quest for an alternative scenario has pointed at the contribution of a nascent millisecond magnetar and/or at the interaction of the supernova ejecta with a circumstellar medium surrounding the progenitor star; however, some of the observed photometric and spectroscopic features of many superluminous supernovae are seemingly reminiscent of a 56Ni-decay contribution. I present the results of the spectrophotometric observational campaigns of three superluminous supernovae and discuss the observational data in the framework of the magnetar and the circumstellar-interaction scenario, and I suggest that some superluminous supernovae might be the UV-optical-NIR counterpart of a magnetorotational instability-driven core collapse.

Speaker: Achille Fiore (Goethe Universität Frankfurt am Main)

one_minute_slide.pdf

35 Microscopic fission collective inertias for astrophysical applications

Nuclear fission is one of the most important nuclear phenomena and arguably its most interesting astrophysical application is in the study of r-process nucleosynthesis. The theoretical description of fission is a challenging quantum many body problem and one such key challenge is the description of collective inertias along the fission path. In most of the fission calculations, the collective inertia is evaluated using cranking approximation which neglects the dynamical residual effects. Recently, a new method for the calculation of collective inertias using finite amplitude method - quasiparticle random phase approximation (FAM-QRPA) method was devoloped which also takes into account the consistent treatment of dynamical effects neglected in cranking approximation [1]. Work is in progress in developing FAM-QRPA approach using the finite range Gogny energy density functionals and axial symmetry preserving Hartree-Fock-Bogoliubov framework to compute collective inertias needed for fission calculations. The obtained results will be then used to compute new fission reaction rates relevant for r-process calculations. This work is supported by International Graduate School (IRTG 2891) Nuclear Photonics.

1. K. Washiyama, N. Hinohara, and T. Nakatsukasa, Phys. Rev. C 103, 014306 (2021)

Speaker: Mr Nithish Kumar Covalam Vijayakumar (Technische Universität Darmstadt)

Poster_Flash#104.pdf

36 The SOCIAL project: measurement of the ${}^{14}\mathrm{N}(p,\gamma){}^{15}\mathrm{O}$ cross section

Solar neutrinos play a significant role in constraining physical conditions in the interior of the Sun and are a unique tool to investigate its core composition. The ${}^{14}\mathrm{N}(p,\gamma){}^{15}\mathrm{O}$ cross section is the dominant error source on neutrino flux predictions. At solar energies ($15 - 50\,\mathrm{keV}$) such a cross-section is too low to be measured directly, therefore current estimates are based on extrapolations of higher-energy data. The SOCIAL project aims at determining the ${}^{14}\mathrm{N}(p,\gamma){}^{15}\mathrm{O}$ reaction rate at astrophysical energies with $5\%$ precision, as requested by Solar models. We take advantage of the much suppressed gamma-ray background achievable in the underground Gran Sasso laboratory to measure the ${}^{14}\mathrm{N}(p,\gamma){}^{15}\mathrm{O}$ cross section in the $50-370\,\mathrm{keV}$ energy range. We deliver an intense proton beam from the LUNA accelerator to a solid nitrogen target. Gamma-rays are detected with a high-efficiency $4\pi$-BGO detector composed of 6 independent segments. The data analysis technique will lead to determine the total and the partial cross sections for individual gamma transitions. An overview of the experimental setup and the preliminary data analysis will be presented.

Speaker: Dr Giulia Gosta (Università degli Studi di Milano and INFN Milano)

NPA_1slide.pdf

NPA-poster.pdf

37 The deep underground "Bellotti Ion Beam Facility" at the Gran Sasso National Laboratories

The Bellotti Ion Beam Facility was inaugurated in 2023. It currently houses a 3.5 MV Singletron accelerator supplied by High Voltage Engineering Europe, installed inside the deep underground Laboratori Nazionali del Gran Sasso (LNGS) in Italy, where the natural cosmic ray flux is reduced by up to six orders of magnitude. The installation of the facility has been supported by the "LUNA-MV Premium Funds" provided by the Italian Ministry of Research and by INFN.

The intense proton, alpha and carbon beams available at the Bellotti Ion Beam Facility are made available to the international scientific community through annual calls for beam time published on the LNGS website.

This presentation will outline the main characteristics of the facility, its operational status and future developments.

Speaker: Matthias Bernhard Junker (Laboratori Nazionali del Gran Sasso - INFN)

122_265_Pitch.pdf

38 Development of the Charge-Exchange Oslo Method and Application Towards Constraining Reaction Rates for Nucleosynthesis of Cosmochronometer ${}^{92}\mathrm{Nb}$

Charge-Exchange (CE) reactions are an important tool for studying the spin-isopin response of nuclei. They can be utilized to obtain information about interactions mediated by the weak nuclear force, such as $\beta$ and electron capture decay. Using the proportionality between Gamow-Teller strength (B(GT)) and the CE differential cross section, B(GT) distributions can be extracted indirectly. Since CE reactions are not limited to a narrow $Q$ value window, they provide information that is complementary to information obtained from $\beta$ and electron capture decay. Such data are necessary for constraining reaction rates that happen in dense and hot astrophysical environments. In the near future, it is planned to combine measurements in which GT strengths are extracted with $\gamma$-decay measurements, utilizing the Oslo method to extract level densities and $\gamma$-ray strength functions, which are also important for constraining astrophysical reaction rates. It is proposed to measure the ${}^{92}\mathrm{Zr}({}^{3}\mathrm{He},\mathrm{t}+\gamma)$ reactions at $420\,\mathrm{MeV}$ in RCNP to develop the Charge-Exchange Oslo (CE-Oslo) method and to extract reaction rates for the nucleosynthesis of cosmochronometer ${}^{92}\mathrm{Nb}$. This high precision study will lay a solid foundation for using the CE-Oslo method in future $(\mathrm{p},\mathrm{n}+\gamma)$ experiments in inverse kinematics with rare isotopes and make it possible to simultaneously extract nuclear level densities (NLDs), $\gamma$-ray strength functions ($\gamma\mathrm{SFs}$), $\beta$-decay strengths and ($\beta$-delayed) neutron decay probabilities ($P_\mathrm{n}$) on neutron-rich unstable nuclei, which are important for several nucleosynthesis processes, including the r, i, $\gamma$, and $\nu$ processes. The high resolution available for $({}^{3}\mathrm{He},\mathrm{t})$ experiments at RCNP will make it possible to extract level densities in two independent manners: by using the Oslo technique and by using the fine-structure analysis. From the measurement on ${}^{92}\mathrm{Zr}$, it will be possible to extract level densities and $\gamma$-ray strength functions which are relevant for the $\gamma$-process in type Ia supernovae and Gamow-Teller strength distributions of relevance for the $\nu$-process in core-collapse supernovae. These astrophysical phenomena are the possible sites for the production of long-lived ${}^{92}\mathrm{Nb}$, which can serve as a cosmochronometer. As an initial test, the CE-Oslo method is being tested on $(\mathrm{t},{}^{3}\mathrm{He}+\gamma)$ data taken previously with the S800 spectrometer in coincidence with the GRETINA $\gamma$-ray detector at FRIB. Preliminary results of the analysis will be shown at the conference.

This research is supported by the US National Science foundation, Grant No. 2209429, "Nuclear Astrophysics at FRIB".

References:
1. R. Zegers, Research Proposal, Submitted to the B-PAC at RCNP (2020)
2. T. Hayakawa et al., Ap.J.Lett. 779, L9 (2013)
3. A. Spyrou et al., Phys. Rev. Lett. 113, 232502 (2014)
4. B. Gao et al., Phys. Rev. C 101, 014308 (2020)

Speaker: Neshad D. Pathirana (Department of Physics and Astronomy, Michigan State University; Facility for Rare Isotope Beams (FRIB), Michigan State University; JINA-CEE)

202-Neshad-one_min_slide.pptx

202-Neshad-Poster.pptx

12:55 Lunch Break

Plenary Session: C: Hydrostatic stellar burning (1).

Convener: Alessandra Fantoni (European Physical Society)

39 Nucleosynthesis and wind yields of Very Massive Stars

The most massive stars provide an essential source of recycled material for young clusters and galaxies. While very massive stars (VMS, $M>100 \,M_\odot$) are relatively rare compared to O stars, they lose disproportionately large amounts of mass already from the onset of core H-burning. In this talk, I will discuss the impact of stellar wind yields from VMS, calculated for a wide range of masses ($50-500\,M_\odot$) at solar metallicity, using the MESA stellar evolution code. We find that for VMS, $95\%$ of the total wind yields are produced already on the main sequence, while only $\sim 5\%$ is supplied by the post-main sequence. This implies that VMS are the primary source of ${}^{26}\mathrm{Al}$ and could be responsible for the observed Galactic ${}^{26}\mathrm{Al}$ enrichment. Interestingly, we find that $200\,M_\odot$ stars eject $100$ times more of each heavy element in their winds than $50\,M_\odot$ stars, and even when weighted by an IMF their wind contribution is still an order of magnitude higher than that of a $50\,M_\odot$ star.

Speaker: Dr Erin Higgins (Armagh Observatory and Planetarium)

EH_Dresden24.pdf

40 Stellar abundances with 3D model atmospheres

The chemical compositions of stars place key constraints on nuclear astrophysics. The most precise way of determining these compositions is through analyses of the absorption lines in the observed star light (stellar spectroscopy). However, the accuracy of standard analyses of Sun-like stars can be limited by various simplifying assumptions. The vast majority of analyses take the atmosphere of the star to be one-dimensional (1D) and hydrostatic. More accurate results can be obtained via three-dimensional (3D) radiation-hydrodynamics simulations. Another common assumption is that of local thermodynamic equilibrium (LTE). For certain lines and stars, the inherent shortcomings of 1D models can mask the impact of departures from LTE; in other words, it is even more important to take non-LTE effects into account when using 3D models. I shall describe this 3D non-LTE approach, and then present examples where its application has altered our understanding of the evolution of the elements in the cosmos.

Speaker: Anish Amarsi (Uppsala University)

draft.pdf

draft.pptx

41 Nuclear astrophysics at LUNA and LUNA-MV

During the last 30 years, the Laboratory for Underground Nuclear Astrophysics (LUNA) investigated many nuclear reactions of interest for cosmological and stellar models, often directly at the relevant Astrophysical energies. Nuclear reactions involved in the Big Bang nucleosynthesis, the p-p and CNO chains, as well as slow neutron capture were studied providing accurate and precise data to the to both the nuclear and astrophysics communities. To study more energetic scenarios as the carbon fusion, a new $3.5\,\mathrm{MV}$ accelerator (LUNA-MV) was installed, commissioned and now in operation at the Bellotti facility of the Gran Sasso Laboratories.

In this talk I will present results of recent LUNA measurements and give an overlook of the current activities and possible outlooks.

Speaker: David Rapagnani (Università degli Studi di Napoli "Federico II")

Rapagnani_LUNA.pdf

42 New results on proton captures on neon isotopes at LUNA

The NeNa-MgAl cycles are involved in the synthesis of Ne, Na, Mg, and Al isotopes. The ${}^{20}\mathrm{Ne}(p,\gamma){}^{21}\mathrm{Na}$ reaction is the slowest reaction of the NeNa cycle and it controls the speed at which the entire cycle proceeds. The ${}^{21}\mathrm{Ne}(p,\gamma){}^{22}\mathrm{Na}$ has a relevant role in the production of the radioactive isotope ${}^{22}\mathrm{Na}$ that is interesting for novae and supernovae. Presently, the ${}^{20}\mathrm{Ne}(p,\gamma){}^{21}\mathrm{Na}$ and ${}^{21}\mathrm{Ne}(p,\gamma){}^{22}\mathrm{Na}$ are carrying larger uncertainties and therefore their reaction rate is affecting the production of the elements in the NeNa cycle and the astrophysical sites of interest.
At the temperatures of interest for AGB stars and novae where the the NeNa cycle play a important role, the ${}^{20}\mathrm{Ne}(p,\gamma){}^{21}\mathrm{Na}$ is dominated by the direct capture component and the $366\,\mathrm{keV}$ resonance, while the ${}^{21}\mathrm{Ne}(p,\gamma){}^{22}\mathrm{Na}$ reaction is governed by several resonances at $E_p = 126 -350\,\mathrm{keV}$. The experiments have been carried out at LUNA (Laboratory for Underground Nuclear Astrophysics), by using the intense proton beam delivered by the $\mathrm{LUNA}~400\,\mathrm{kV}$ accelerator and a windowless differential-pumping gas target. The products of the reaction were detected with two high-purity germanium detectors. The first results on those two reaction together with a detailed evaluation of their astrophysical impact will be presented.

Speaker: Antonio Caciolli (University and INFN of Padova)

Caciolli_NPA2024.pdf

Poster Flashes: C

Every poster presenter has 1 minutes to present 1 slide summarizing the poster

43 Re-visiting the role of short-range correlations on neutron star properties

Speaker: Anagh Venneti (Department of Physics BITS Hyderabad India)

023_213_Pitch.pdf

44 Unraveling the global behavior of equation of state by explicit finite nuclei constraints

We obtain posterior distribution of equations of state (EOSs) across a broad range of density by imposing explicitly the constraints from precisely measured fundamental properties of finite nuclei, in combination with experimental data from heavy-ion collisions and astrophysical observations of radius, tidal deformability and minimum-maximum mass of neutron stars. The acquired EOSs exhibit a distinct behavior compared to those usually obtained by imposing the finite nuclei constraints implicitly through empirical values of selected key parameters describing symmetric nuclear matter and symmetry energy in the vicinity of saturation densities. The explicit treatment of finite nuclei constraints yields softer EOSs at low densities which eventually become stiffer to meet the maximum mass criteria. The radius measurements derived from NICER and HESS J1731-347 exhibit favorable agreement with the posterior distribution of radius determined through our explicitly constrained EOSs. The Kullback-Leibler divergence has been used to perform a quantitative comparison of the distributions of the EOSs resulting from implicit and explicit finite nuclei constraints.

Speaker: Anagh Venneti (Department of Physics, Birla Institute of Technology and Science Pilani, Hyderabad Campus, Hyderabad-500078,India)

45 Resolving the discrepancies in the spectroscopy of ${}^{39}$Ca for the $^{38}$K($p$,$\gamma$)$^{39}$Ca reaction

Elemental abundances are excellent probes of classical novae (CN). Sensitivity studies show that $^{38}$K($p$,$\gamma$)$^{39}$Ca reaction-rate uncertainties modify the abundance of calcium by a factor of 60 in CN ejecta. Existing direct and indirect measurements are in contradiction concerning the energies and strengths of important resonances in the $^{38}$K($p$,$\gamma$)$^{39}$Ca reaction. Direct measurements of the lowest three known $\ell = 0$ resonances at $E_\mathrm{r} = 386, 515, \text{ and } 679\,\mathrm{keV}$ have greatly reduced the uncertainties on the reaction rate for this reaction. A subsequent $^{40}$Ca($^{3}$He,$^4$He)$^{39}$Ca experiment using the SplitPole at TUNL concluded that one of the resonances ($E_\mathrm{r}$ = 701.3 or $E_\mathrm{r}$ = 679 keV depending on the source of the nuclear data) may have been misplaced in the DRAGON target during the direct measurement and that tentative new states at $E_\mathrm{x} = 5908, 6001, \text{ and } 6083\,\mathrm{keV}$ ($E_\mathrm{r} = 137, 230, \text{ and } 312\,\mathrm{keV}$) could correspond to important resonances in $^{38}$K($p$,$\gamma$)$^{39}$Ca. To resolve these, $^{39}$Ca was studied using the $^{40}$Ca($p,d$)$^{39}$Ca reaction at forward angles with a proton beam energy of $66\,\mathrm{MeV}$ using the K600 magnetic spectrometer. These measurements are aimed at verifying the properties of levels in the region where discrepancies between various experiments persist. Preliminary results will be presented.

Speaker: Sifundo Binda (University of the Witwatersrand and iThemba LABS)

Binda-NPA-XI-pitch.pdf

46 Experimental studies on the optical spectrum of the heavy r-process nuclide Cf-254 and its neighbors

The spontaneously fissioning isotope californium-254 is predicted to have a high impact on the brightness of electromagnetic transients associated with neutron star mergers on the timescale of 10 to 250 days, due to its 60-day half-life. [Zhu et al., AJL 863, L23 (2018)]. Experimental information on Cf-254 is scarce, owing to limited production capabilities in the laboratory. We have performed laser spectroscopy on this and neighboring isotopes at the RISIKO mass separator at Johannes Gutenberg University Mainz (JGU), Germany. For this, Cm targets were neutron-irradiated at Oak Ridge National Laboratory (ORNL), TN, USA, to breed Es-253,254. After the chemical separation at ORNL the Es fraction, which also contained some Cf-252, was shipped to JGU, via Florida State University, FL, USA, and then sent to Institut Laue-Langevin, Grenoble, France, for a second irradiation to produce more neutron-rich isotopes including, Cf-253 and Cf-254. The hyperfine structure of the $420\,\mathrm{nm}$ ground-state transition in Cf-253 and the isotope shift of Cf-254 in the $417\,\mathrm{nm}$ and $420\,\mathrm{nm}$ ground-state transitions were determined with high resolution down to $140\,\mathrm{MHz}$. These data provide a basis for a King plot analysis of the optical spectrum of Cf-254 based on known data of lighter californium isotopes.

Speaker: Mr Sebastian Berndt (Johannes Gutenberg Universität Mainz, 55099 Mainz, Germany)

Poster_Pitch_NPAXI_Cf254_id80.pdf

47 Exploring late stages of massive stars evolution in the context of new precise nuclear reaction rates

In recent years, new experimental determinations of nuclear reaction rates relevant to astrophysics have been obtained using experimental (direct and indirect) and theoretical methods, highlighting specific trends such as the unexpected fusion hindrance phenomenon for ions or multiple resonances. Especially, a precise determination of the nuclear reaction rates is a crucial ingredient in understanding stellar evolution using stellar evolution models. We now need to take into account these new results, which can provide one of the keys to a better understanding of stellar and chemical evolutions.

New direct measurements of the $^{12}$C+$^{12}$C nuclear reaction at very low energies have been obtained by the STELLA collaboration in France, paving the way for improvements in stellar evolution modelling. Using the evolution code GENEC, we computed a grid of models (8-30 M$_{\odot}$) including rotation. We show the change of nuclear rates impacts the core properties, burning lifetime and nucleosynthesis. We highlight an enhanced effect due to rotation and a strong dependence on the stellar mass related to the observed resonance (Dumont 2024, revised). Finally, we will discuss the potential hindrance effects for the $^{12}$C+$^{16}$O and $^{16}$O+$^{16}$O nuclear reactions involved in later evolutionary stages, which will be measured as part of the CarbOx project.

Speaker: Thibaut Dumont (University of Strasbourg - IPHC)

PitchSlide_Dumont.pdf

48 321D modelling of the interplay between turbulence and nuclear reactions in massive stars

Given the key role massive stars and core-collapse supernovae play in the Universe, developing theoretical models of massive stars and their final collapse is critical. Massive stars are complex 3D objects involving a wide range of interesting physical processes like convection. Stellar models would thus ideally be three-dimensional (3D) (magneto-)hydrodynamic models that include all the relevant physics. These 3D hydrodynamic models, however, must use time steps that are many orders of magnitude shorter than the lifetime of stars. This explains why most stellar evolution models are limited to 1D (e.g. GENEC, MESA codes), equivalent to limiting models to spherical symmetry (or averages). These 1D models have wide ranging applications in astrophysics due to the importance of massive stars. The predictive power of 1D models, however, is crippled by 1D prescriptions of 3D phenomena containing free parameters that need to be calibrated using observations. In this talk, I will present our recent efforts to study convection and its interplay with nuclear reactions in 3D. I will in particular focus on cases where deviations from spherical symmetry are expected (e.g. shell mergers) and discuss how these 3D simulations can be used to improve 1D models.

Speaker: Raphael Hirschi (Keele University)

NPA2024_Hirschi_1slide_321D.pdf

49 New half-lives and $\beta$-delayed neutron branchings for Ba to Nd nuclei (A$\sim$160) for r-process rare-earth nucleosynthesis

The rapid neutron capture process (r-process) is a key mechanism responsible for producing nearly half of the nuclei heavier than iron in explosive scenarios. In the solar-system abundance pattern, the Rare-Earth Peak (REP) around mass number $A = 160$ represents a significant feature resulting from freeze-out during the final stages of neutron exposure. The BRIKEN collaboration [1] conducted extensive measurements of $\beta$-decay properties of nuclei of interest to better understand the r-process at the Radioactive Isotope Beam Factory (RIBF), RIKEN Nishina Center, Japan. Our study focuses on the Barium to Neodymium region crucial for REP r-process nucleosynthesis [2,3]. In this contribution, we present the final experimental results from the BRIKEN-REP experiment, which yielded new $T_{1/2}$ and $P_{1n}$ branching ratios. Furthermore, we discuss the implications of these findings for global models of nuclear structure, aiming to refine theoretical predictions and enhance our understanding of REP r-process nucleosynthesis.

[1] J.L. Tain et. al , Acta Physica Polonica B {49(03), 417 $-$ 428 (2018).
[2] M. R. Mumpower et al , Phys. Rev. C 85, 045801 (2012).
[3] A. Arcones and G. Martinez Pinedo , Phys. Rev. C 83, 045809 (2011).

Speaker: Max Pallas I Solis (Universitat Politècnica de Catalunya (UPC))

NPA_MaxPallas_ID260.pdf

NPAPoster_MaxPallas_ID260.pdf

50 Investigating the Effects of Convective Boundary Mixing on Massive Stars at Low Z

Massive stars are not well enough understood given the important role their evolution and fates play in Galactic Chemical Evolution (GCE). One key uncertainty is convective boundary mixing (CBM), which encompasses the processes by which materials mix across the edge of convective turbulent regions inside stars. As a result of its effects on stellar structure during evolution, CBM also affects nucleosynthesis and consequently stellar yields. To investigate the importance of CBM we have computed two grids of stellar models at $Z=10^{-3}$ and two different strengths of CBM using the MESA code. The first being the typical CBM value used in literature and the second is based on the results of 3D convection simulations. In this talk, we will present a comparison of the structure of massive stars both during their evolution and at the end of their lives for these two different strengths of CBM to assess the impact of CBM on stellar evolution, SN progenitors and nucleosynthesis with a particular emphasis on the mergers of different burning shells.

Speaker: Emily Whitehead (Keele University)

114_262_Pitch.pdf

51 Multimessenger emission of Accretion-Induced Collapse events

An white dwarf (WD) which accreates enough mass to surpass the Chandrasekhar limit will became unstable and will initiate a collapse stage due to its own gravity. Depending on their composition and their accretion history, the collapsing WD may trigger a thermonuclear explosion (and lead to a Supernova Ia) or not. In the latter case, the collapse, completely driven by the electron capture process, will proceed until the central density reaches nuclear saturation density when the core of the collapsing star will expand abruptly and push its outer layers in an outwards motion. To the second scenario, where a proton-neutron star is left as an remnant, it is given the name of accretion-induced collapse (AIC). Due to the accretion history of AICs and their highly spinning and (probably) magnetized remnant, these events have historically been proposed as the engines of short gamma-ray bursts and millisecond pulsars. AIC are also related to the nucleosynthesis of rare neutron-rich isotope, due to the (initially) low electron-fraction content of their ejecta. In this talk, we will explore different aspects of AICs, exploring for example the imprint of the progenitor angular momentum on their multimessenger emission.

Speaker: Luis Felipe Longo Micchi (Friedrich-Schiller Universitat)

121_264_Pitch.pdf

52 S-Process Nucleosynthesis in and from AGB Stars

The nucleosynthetic s-process occurring in AGB stars from 1-6 M is responsible for creating half of the heavy elements in the universe. The s-process can be traced directly through AGB stars, or indirectly through their binary companions (Ba, CEMP-s, CH stars), as AGBs will dredge s-process material to the surface and deposit this material onto the companion.

We present data for 30 stars including AGB, CEMP-s, Ba, and CH stars. We derive atmospheric parameters using ATHOS and compute 1D LTE abundances with MOOG, focusing on elements created by thermally pulsing AGB stars (C, Sr, Y, Zr, Mo, Ba, La, Ce, Nd, Pb), and Eu. We monitor RVs to investigate binary properties.

Comparing our abundances to FRUITY yields we estimate masses of AGB stars, and we investigate correlations in abundance space. With detailed modelling of orbits using the ELC program, we estimate dynamical masses and orbital parameters. For our systems and data from Hansen+ 2019 and Placco+ 2014, we investigate efficiencies of AGB wind mass transfer and stellar mixing processes by simulating binary accretion using the STARS code. Our results show correlations between AGB and companion masses from abundance patterns and dynamical masses. This work has implications for galactic chemical evolution.

Speaker: Alexander Jordan Dimoff (Max Planck Institute für Astronomie)

123_266_Pitch.pdf

53 Fully calibrated lanthanide atomic data for 3D kilonova modeling

With the detection of multiple neutron-star merger events in the last few years, the need for a more comprehensive understanding of nuclear and atomic properties has become increasingly important. Despite our current understanding, there are still large discrepancies in the opacities obtained from different codes and methods. These discrepancies lead to variations in the location and strength or absorption and emission features in radiative transfer models and prevent a firm identification of r-process products. To address this issue, we developed an optimisation technique for energy levels and oscillator strengths consistent with available experimental data. With this novel method, we can increase the accuracy of calculations while reducing the computational cost, finally making it possible to apply the method to all lanthanides instead of focusing on single ions.

We will report on converged large-scale atomic structure calculations of all singly and doubly ionised lanthanides with greatly improved transition wavelength accuracy compared to previous works. The impact of our new atomic data set on realistic 3D radiative transfer calculations and prospects of r-process signature identification will be investigated.

This work is supported by the European Research Council (ERC) under
the European Union’s Horizon2020 research and innovation programme
(ERC Advanced Grant KILONOVA No.885281)

Speaker: Andreas Floers (GSI Helmholtzzentrum für Schwerionenforschung)

Poster_Flash_Floers.pdf

54 The quest for detection of $^{182}$Hf in Earth’s archives - new techniques in Accelerator Mass Spectrometry for the search of live nucleosynthesis signatures

Accelerator mass spectrometry (AMS) is commonly the most sensitive technique for detection of long-lived isotopes and has allowed identification of $^{60}$Fe and $^{244}$Pu signals in terrestrial and lunar archives from recent nearby nucleosynthesis.
Belonging to the middle-mass region of r-process nuclides, $^{182}$Hf (T$_{1/2}$=8.9$\,$Ma) could potentially be produced in different scenarios to those for $^{244}$Pu. However, AMS detection of astrophysical $^{182}$Hf has failed up to now due to the strong interference from its ubiquitous stable isobar $^{182}$W. Based on various yield- and elemental-ratio-calculations for possible $^{182}$Hf production scenarios, the estimated $^{182}$Hf/Hf signal intensity is at most a few times 10$^{−13}$, about two orders of magnitude below classical AMS sensitivity limits.

The novel Ion-Laser InterAction Mass Spectrometry (ILIAMS) technique achieves near-complete suppression of isobars via selective laser photodetachment and chemical reactions of decelerated anion beams in a gas-filled radio frequency quadrupole. It enables suppression of $^{182}$WF$_5$$^−$ vs. $^{182}$HfF$_5$$^−$ by >10$^5$ resulting in a W-corrected blank value of $^{182}$Hf/$^{180}$Hf=(3.4$\pm$2.1)$\times$10$^{–14}$.

We will highlight the potential of ILIAMS for sensitive detection of previously inaccessible long-lived radioisotopes and discuss ways to proceed in order to detect $^{182}$Hf at astrophysical levels including the challenges this poses in chemical sample preparation of HfF$_4$ from 100$\,$gram-amounts of deep-sea archives.

Speaker: Martin Martschini (University of Vienna, Faculty of Physics – Isotope Physics, VERA Laboratory, Vienna, Austria)

Poster Pitch #128_Martschini_182Hf.pdf

55 Results of cross-section measurements of proton-capture reactions on stable Rubidium isotopes

The existence of some stable neutron deficient nuclei - the p nuclei - can not be explained by neutron-capture processes [1]. Therefore, other types of reactions - dominantly photodisintegration reactions - come into play. This is called the $\gamma$ process. Statistical model calculations play a crucial role in modelling this process as cross sections for many of these photodisintegration reactions are not known trough experiments.

Two in-beam experiments were performed at the University of Cologne's high-efficiency HPGe $\gamma$-ray spectrometer HORUS to study the $^{85,87}$Rb$(p, \gamma)^{86,88}$Sr reactions. A 10 MV FN Tandem accelerator provided proton beams between $E_p = 2$ and $5$ MeV. Total cross-section values were determined for six different proton-beam energies for the $^{87}$Rb$(p, \gamma)^{88}$Sr reaction and for three different proton-beam energies for the $^{85}$Rb$(p, \gamma)^{86}$Sr reaction. These first experimental cross-section values for the $^{85,87}$Rb$(p, \gamma)^{86,88}$Sr reactions help to constrain the nuclear physics input for statistical model calculations.

Supported by the DFG (ZI 510/8-2).

[1]T. Rauscher \textit{et al}., Rep. Prog. Phys. \textbf{76} (2013) 066201.

Speaker: Ms Svenja Wilden (University of Cologne, Institute for Nuclear Physics)

130_270_Pitch.pdf

56 Search for r-process Pu-244 in the K-Pg boundary layer

The K-Pg (Cretaceous–Paleogene) boundary at 66 Ma marks one of five major mass extinctions in Earth’s fossil history. Based on strong enrichments of platinum-group elements, Alvarez et al. [1], in 1980, suggested that the impact of a large asteroid was responsible for the K/Pg event. To exclude other causes for the mass extinction, e.g., a nearby supernova(SN)-explosion, they also searched for a long-lived radionuclide, $^{244}$Pu (t$_{1/2}$=81 Myr), assuming that this is predominantly produced and ejected in SNe. No $^{244}$Pu was detected, leaving an impact as the most plausible cause. This was also confirmed by discovering the Chicxulub impact structure.
However, since 1980, strong evidence evolved that heavy r-process elements, like $^{244}$Pu, are produced in rare explosive events [2]. Furthermore, the method of Accelerator Mass Spectrometry has since emerged with superior detection efficiency for $^{244}$Pu [3]. The enormous gain in sensitivity prompted us to reinvestigate the $^{244}$Pu content in the K-Pg boundary layer, despite the overwhelming evidence for an asteroid impact. However, no enhanced $^{244}$Pu concentration was found, again ruling out the SN hypothesis.
[1] Alvarez et al., Science 208 (1980) 1095. [2] Wallner et al., Science 372 (2021) 742. [3] Fields, Wallner, Annu. Rev. Nucl. Part. Sci. 73 (2023) 365.

Speaker: Sebastian Fichter (Helmholtz-Zentrum Dresden-Rossendorf)

NPA-2024_Poster-Flash_SF.pdf

15:55 Coffee Break

Plenary Session: D: Dense matter (1). & New tools and techniques (1).

Convener: Alison Laird (University of York)

57 Nuclear physics constraints on the equation of state of dense matter

The determination of the equation of state (EoS) of dense matter is a challenge in nuclear astrophysics, and particularly for the modelling of compact obects such as supernovae and neutron stars (NSs). Indeed, a consistent description of the different states of matter encountered in these stellar objects spanning a wide range of densities, temperatures, and isospin asymmetries is a difficult task. The EoS is however important in compact-star modelling since it allows to relate the prediction of astrophysical observables to microphysical properties of dense matter. In particular, for old (mature), slowly rotating, and isolated NSs, this connection indeed mainly relies on the knowledge of the EoS.

In this contribution, I will give a brief introduction on the dense-matter EoS, and specifically on the EoS for NSs. Various constraints will be discussed, focussing on those coming from nuclear physics (theory and experiments). The prediction of NS observables obtained with different EoSs (with their associated uncertainties) will be discussed in connection with recent (multi-messenger) astrophysical observations.

Speaker: Anthea Fantina (Grand Accélérateur National d'Ions Lourds (GANIL))

Fantina_2024_09_16_NPA-XI.pdf

58 Constraints on Nucleosynthesis Processes through Measurements in the Nuclear Quasi-Continuum

The gamma-ray decay of nuclear states in the quasi-continuum provides significant constraints on nucleosynthesis processes. In particular, measurements of Nuclear Level Densities (NLDs) and Photon Strength Functions (PSFs) have and will continue to play a central role as these are inputs for the statistical Hauser-Feshbach model. This facilitates the extraction of neutron-capture cross-section data even for nuclei where direct measurements are not feasible. Now, PSF and NLD measurements in previously inaccessible regions of the nuclear chart have become possible due to many facilities worldwide offering enhanced or new state-of-the-art research infrastructure. These range from significant increases in efficiencies for particle and gamma-ray detectors to new or upgraded radioactive ion beam facilities. In parallel, several new experimental and analytical techniques have been developed, enabling more reliable PSF and NLD studies. This collective progress will undoubtedly yield unprecedented experimental constraints to nucleosynthesis processes.
I will provide an overview of recent developments in particular the Shape method, which allows for a model-independent extraction of NLDs and PSFs even for nuclei away from stability. Furthermore, I will discuss how our understanding of observed isotopic abundances can be enhanced through the measurement of PSFs and NLDs, using the i-process nucleus 67Ni as an example.

Speaker: Mathis Wiedeking (Lawrence Berkeley National Laboratory)

59 Trojan Horse method for nuclear astrophysics

Over the past decades nuclear physicists have been trying to measure the rates of the most relevant nuclear reactions, which are responsible for the element nucleosynthesis, but there is still considerable uncertainty about their values.
This is because their reaction rates are extremely small, making it difficult for them to be measured directly in the laboratory. Indeed, although e.g. the stellar temperatures are of the order of hundred million degrees, they correspond to sub-Coulomb energies. As a consequence, the Coulomb barrier causes a strong suppression of the cross-section, which drops exponentially with decreasing energy.
In addition, the electron screening effect due to the electrons surrounding the interacting ions prevents one to measure the bare nucleus cross-section.
Typically, the standard way to determine the bare nucleus cross-section at the astrophysics relevant energies consists in a simple extrapolation of available higher energy data. This is done by means of the definition of the astrophysical S(E) factor, which essentially represents the cross-section free of Coulomb suppression. However, the extrapolation may introduce additional uncertainties due for instance to the presence of unexpected resonances or to high energy tails of sub-threshold resonances.
A valid alternative approach is represented by indirect methods developed to overcome some of the limits of measuring at astrophysical energies. A common feature shared by indirect methods is to replace the relevant two-body reaction at low energies by a high-energy reaction usually with a three-body final state.
In particular, the Trojan Horse Method (THM) is applied to charged particle reactions either resonant or non-resonant and allows to extract the energy-dependence of their S(E) factors. I will recall the basic ideas of THM and show a step-by-step analysis of a measurement relevant for the Big Bang Nucleosynthesis scenario and its use.

Speaker: Roberta Spartà (Laboratori Nazionali del Sud - INFN & University of Enna "Kore")

THM4NA-upload-Sparta.pdf

60 The effect of dark matter on compact stars and constraints we put on strongly interacting matter at high densities

We study the impact of asymmetric fermionic and bosonic dark matter on neutron star properties, including tidal deformability, maximum masses, radii, thermal evolution, a moment of inertia, quasi-universal relations, etc. The conditions at which dark matter particles tend to condense in the core of the star or create an extended halo are presented. We show that dark matter condensed in a core leads to a decrease of the total gravitational mass and tidal deformability compared to a pure baryonic star, which we will perceive as an effective softening of the equation of state. On the other hand, the presence of a dark matter halo increases those observable quantities. Thus, observational data on compact stars could be affected by accumulated dark matter and, consequently, constraints we put on strongly interacting matter at high densities. We will discuss how the ongoing and future X-ray, radio, and GW observations could shed light on dark matter admixed compact stars and put multi-messenger constraints on its effect. A special emphasis will be given to the next-generation gravitational wave detectors.

Speaker: Violetta Sagun (University of Coimbra)

NPA-XI_Sagun.pdf

61 Influence of Density Dependence of Symmetry Energy on Astrophysical S-Factor in Heavy-Ion Fusion Reactions

The nuclear symmetry energy and its density dependence play a crucial role in defining the properties of a wide range of systems, spanning from asymmetric nuclei to neutron stars and various other astrophysical phenomena. Motivated by recent advancements, particularly the precise determination of neutron skin thickness for ${}^{208}\mathrm{Pb}$ and ${}^{48}\mathrm{Ca}$ nuclei through PREX-II and CREX, this study addresses the unresolved density dependence issue of symmetry energy, specifically focusing on the recent estimate of the slope (L0) at saturation density. We explore the density dependence of symmetry energy in sub-barrier fusion cross-sections and astrophysical $S$-factors for asymmetric nuclei. Utilizing non-relativistic and relativistic mean-field models, we generate nucleon densities across a spectrum of neutron skin thickness or L0 values. Results for O, Ca, Ni, and Sn isotopes reveal the impact of symmetry energy behaviour and neutron skin thickness on barrier parameters, cross-sections, and astrophysical $S$-factors. Particularly, cross-sections for neutron-rich nuclei exhibit pronounced dependence on symmetry energy and neutron skin thickness. Increased skin thickness lowers barrier height and width, significantly enhancing $S$-factor values. This investigation offers insights into the complex interplay of density dependence in symmetry energy and reaction parameters, contributing to our understanding of asymmetric nuclei in sub-barrier fusion reactions.

Speaker: G. Saxena (Govt. Women Engineering College, Ajmer-305002, Rajasthan, India)

1755_Saxena.pdf

Poster Flashes: D

Every poster presenter has 1 minutes to present 1 slide summarizing the poster

62 First evaluation of the $^{17}$O(p,$\gamma$)$^{18}$F 65 keV resonance strength by direct measurement at LUNA

The $^{17}$O(p,$\gamma$)$^{18}$F reaction plays a key role in the hydrogen burning in CNO cycle. At temperatures of interest for the H-shell burning in AGB stars, the reaction rate is dominated by the $E_\mathrm{c.m.}=65\,\mathrm{keV}$ resonance.

The strength of this resonance is presently determined only through indirect techniques, with a literature value $\omega\gamma = (16 \pm 3)\,\mathrm{neV}$, leading to an expected counting rate of $0.3\,\mathrm{reactions}/\mathrm{C}$ for typical experimental quantities.

The LUNA collaboration has recently performed a new direct measurement of the $^{17}\mathrm{O}(p,\gamma){}^{18}\mathrm{F}$ cross section focused on the $65\,\mathrm{keV}$ resonance taking advantage of the ultra-low background of the deep underground Laboratori Nazionali del Gran Sasso (LNGS, Italy) and of a high stable intense proton beam ($ \left< I \right> = 200\,\mu\mathrm{A} $) provided by the LUNA400 accelerator. For this purpose, a high sensitivity and high efficiency setup based on a segmented $4\pi$ BGO detector was developed. All these experimental efforts allowed, for the first time ever, the evaluation of the $65\,\mathrm{keV}$ resonance strength by a direct technique. Moreover, also the $\Gamma_p$ width was calculated, confirming the results of the ${}^{17}\mathrm{O}(p,\alpha){}^{14}\mathrm{N}$ $65\,\mathrm{keV}$ resonance measured in a previous LUNA experiment.

In the talk, the results of the new LUNA measurement will be presented.

Speaker: Riccardo Maria Gesue' (Gran Sasso Science Institute, INFN LNGS)

027_216_Pitch.pdf

63 The direct determination of the cross section of the 12C + 12C reaction at astrophysical energies

Carbon burning is the third stage of stellar evolution determining the final destiny of massive stars and of low-mass stars in close binary systems. Only stars with a mass larger than a critical value $M^{*}_{up}\sim10M_\odot$, can ignite C in non-degenerate conditions and proceed to the next advanced burning stages up to the formation of a gravitationally unstable iron core. Various final destinies are possible, among which a direct collapse into a black hole or the formation of a neutron star followed by the violent ejection of the external layers (type II SN). Less massive stars $M

$^{12}C+^{12}C$ fusion reactions were investigated in a wide energy range, down to 2.1MeV, still above the astrophysical energies.
Only indirect measurement covers those energies with contradictory results. A direct measurement down to the Gamow peak is therefore crucial.

The aim of the LUNA collaboration is the direct determination of the cross section of the $^{12}C+^{12}C$ reaction at astrophysical energies through $\gamma$ spectroscopy at LNGS. Here a devoted setup is being developed to reach an extremely low background condition. The experiment will make use of the new MV accelerator available at the Bellotti Ion Beam Facility at LNGS, in the context of the LUNA MV research project. This accelerator is capable of producing a high intensity carbon beam ($150\mu A$ for a beam of $^{12}C^+$ and $50p\mu A$ for a beam of $^{12}C^{++}$) with great energy resolution and stability. The detection setup will be made of several NaI scintillators and an HpGe. NaI detectors will be placed in a compact arrangement around the HpGe, covering a $\sim3.5\pi$ solid angle: such a configuration guarantees a high detection efficiency, while preserving the excellent HpGe resolution (1.2keV at 1.33MeV).
The NaI configuration will also function as an active veto for Compton, environmental radioactivity and beam-induced background events.
The detectors array will be placed in a 2cm thick copper shielding surrounded by a 25cm lead shielding which will further reduce the
environmental background of more than 2 orders of magnitude.

With this setup, we'll also be able to measure the level density of $^{24}Mg$
through the de-excitation of $^{20}Ne$ and $^{23}Na$ nuclei.
This will allow us
to explore the possible cluster structures of the $^{24}Mg$ nucleus. In
particular, we'll be able to examine the $E_{cm}=1.5\,MeV\,-\,4\,MeV$ energy
window (15.44 MeV to 17.94 MeV considering the Q-value), where the
cluster states could be found.

With my contribution I will present an overview of the experiment setup and development, together
with details on Geant4 simulations and preliminary measurements.

Speaker: Riccardo Maria Gesue' (Gran Sasso Science Institute, INFN LNGS)

178_301_Pitch.pdf

64 Understanding 22Na cosmic abundance

We have developed a new, extremely precise experimental approach for measuring the lifetimes of excited states. This method uses gamma-tracking detectors with high resolution in energy and angle.

This method has been used at GANIL, France, to measure the lifetimes of 23Mg excited states. The gamma rays were measured with the AGATA gamma-ray detector, and the ejectiles from the 3He(24Mg,alpha)23Mg* reaction were measured in coincidence with the VAMOS++ spectrometer. This measurement was used to constrain the rate of the 22Na(p,gamma)23Mg reaction, and to determine the maximum detection distance of the 22Na produced in novae.

Ref: Fougères, Chloé, et al. "Search for 22Na in novae supported by a novel method for measuring femtosecond nuclear lifetimes." Nature communications 14.1 (2023): 4536.

Speaker: Francois de Oliveira Santos (GANIL)

poster_ pitch _oliveira_#138.pdf

65 Stelle Sulla Terra: The advantages of making science accessible

Nuclear astrophysics is a field of research that lends itself to an engaging dissemination thanks to its interdisciplinary nature. It is important to involve blind or deaf individuals in these moments of dissemination to an even greater extent. The project ‘Stelle sulla Terra’ at the University of Padua aims to achieve this by reproducing a scaled model of the ‘Bellotti’ IBF facility and creating other tactile materials and videos using sign language.”

Speaker: Antonio Caciolli (University and INFN of Padova)

140_277_Pitch.pdf

66 Comparing Radiative Transfer Methods for Kilonovae

The electromagnetic signals from the kilonova AT2017gfo provide an opportunity to study an astrophysical site of the r-process which produced about half of all nuclei heavier than iron. In order to be able to connect kilonova light curve and spectral properties to the ejecta dynamics it is important to address the role of the individual simplifying assumptions commonly used in theoretical modelling. Fully self-consistent radiative transfer Monte Carlo simulations are nowadays possible. However, due to computational limitations and the need to cover a large parameter space it is important to develop fast and accurate modelling pipelines.

We compare two different methods for simulating kilonova light curves based on two-dimensional simulations of the ejecta dynamics: Monte Carlo radiative transfer (ARTIS code) and a two-moment scheme adopting the M1 approximation (ALCAR code). By this, we are able to benchmark the computationally cheap ALCAR code against the more expensive ARTIS code. Furthermore, we benchmark commonly used approximations for the thermalization of radiative decay products against fully microscopic and local description of the energy deposition.

This work is supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (ERC Advanced Grant KILONOVA No. 885281).

Speaker: Gerrit Leck (GSI Helmholtzzentrum für Schwerionenforschung GmbH)

143_278_Pitch.pdf

67 Homogeneous analysis of 10 highly r-process enhanced stars

A small fraction of old, metal-poor stars exhibits significant enhancement in elements produced through the rapid neutron capture (r-) process, offering a unique laboratory to investigate this process. The R-Process Alliance's initial data release uncovered numerous highly r-processed (r-II) stars. In my work I delve into a detailed chemical analysis of ten such stars, utilizing high-quality spectra and examining over 2000 absorption lines spanning 330 to 940 nm across 49 chemical species. This meticulous examination yields the most comprehensive and uniformly analyzed collection of r-II stars to date. A systematic approach ensures reliable abundance distributions, facilitating the identification of potential variations in chemical compositions among the stars, indicative of r-process variability. The research aims to discern patterns, differentiate genuine abundance disparities from instances of r-process Universality, and utilize these findings to constrain r-process site and nucleosynthesis pathways. Two specific regions of elements are investigated: the region from Ru-Ag, where signatures of fission fragment deposition have recently been discovered by Ian Roederer and published in Science (Roederer, 2023), and the region of the third peak elements Os and Ir, which is still poorly explored in these stars.

Speaker: Mila Racca (Stockholm University)

146_281_Pitch.pdf

68 Measurement of ${}^{26}\mathrm{Al}(n,p)$ and ${}^{26}\mathrm{Al}(n,\alpha)$ Cross Sections in Supernova Temperatures

The radioisotope ${}^{26}\mathrm{Al}$ plays a crucial role in understanding the origins of cosmic elements, particularly at active nucleosynthesis sites such as supernovae and massive star-forming regions. Its characteristic $1809\,\mathrm{keV}$ $\gamma$-ray emission, observed by gamma telescopes, serves as direct evidence of ongoing nucleosynthesis processes. Neutron-induced reactions, specifically the ${}^{26}\mathrm{Al}(n,p)$ and ${}^{26}\mathrm{Al}(n,\alpha)$ reactions, have been identified as key contributors to the ${}^{26}\mathrm{Al}$ abundance in core-collapse supernova ejecta.

Despite recent progress in measuring these reaction rates up to temperatures of $\sim 1\,\mathrm{GK}$, which are relevant to some ${}^{26}\mathrm{Al}$ creation sites, it remains insufficient for explosive scenarios occurring at temperatures between 1.5 and $3.5\,\mathrm{GK}$. Experimental data for these temperatures are currently lacking due to several challenges. These include the necessity for a powerful neutron source at the relevant energies, constraints on radioactive sample size, and difficulty measuring outgoing charged particles in high radiation environments.

In this study, we propose a novel experimental approach using the ${}^{7}\mathrm{Li}(p,n)$ reaction to generate broad-energy neutron beams. Coupled with a gaseous Micromegas detector, this setup will enable comprehensive measurement of ${}^{26}\mathrm{Al}(n,p)$ and ${}^{26}\mathrm{Al}(n,\alpha)$ reaction rates across the relevant energy range. Our study aims to advance cosmic nucleosynthesis understanding and enhance astrophysical modeling by bridging this knowledge gap.

Speaker: Mr Akiva Green (Hebrew University of Jerusalem)

150_282_Pitch.pdf

69 Probing the deconfinement phase transition in hybrid stars with the fastest-spinning millisecond pulsars

We study the properties of hybrid stars containing a color superconducting quark matter phase in their cores, described by the chirally symmetric formulation of the confining relativistic density functional approach. It is shown that depending on the dimensionless vector and diquark couplings of quark matter, the characteristics of the deconfinement phase transition are varied, allowing us to study the relation between those characteristics and mass-radius relations. Moreover, we show that the quark matter equation of state (EoS) can be nicely fitted by the Alford-Braby-Paris-Reddy model that gives a simple functional dependence between the most important parameters of the EoS and microscopic parameters of the initial Lagrangian. The developed approach is utilized for analyzing spinodal instability of quark matter and constructing hybrid quark-hadron EoS. Based on it, we analyze the special points of the mass-radius diagram in which several mass-radius curves intersect. Using the found empirical relation between the mass of the special point, the maximum mass of the mass-radius curve, and the onset mass of quark deconfinement, we constrain the range of vector and diquark couplings of the quark matter model. In addition, we construct a family of curves, which allow us to describe the black widow pulsar PSR J0952-0607.

Speaker: Christoph Gartlein (University of Lisbon)

Flash talk_new.pdf

70 Cosmogenic and Interstellar Radionuclides in Lunar Soil

The astrophysical site of the r-process remains an open question in nuclear astrophysics. Pure r-process radionuclides present in the solar system today that cannot originate from primordial events due to their comparably short half-lives (e.g. $^{\textrm{244}}$Pu t$_{1/2}\,\sim\,$81$\,$Myr) act as fingerprints of recent r-process events in the solar neighbourhood. The discovery of live $^{\textrm{244}}$Pu via single-atom counting with accelerator mass spectrometry (AMS) in deep-sea ferromanganese crusts has recently confirmed such r-process activity. We now aim to extend our search for interstellar $^{\textrm{244}}$Pu and also supernova-produced $^{\textrm{60}}$Fe (t$_{1/2}\,$=$\,$2.6$\,$Myr) to a different archive, lunar soil, which allows to map out the interstellar influx up to hundreds of millions of years ago. The proper characterization of the soil's exposure history and composition is important here. Alongside various analytical methods we measure cosmogenic radionuclides with half-lives in the order of million years via AMS. $^{\textrm{10}}$Be, $^{\textrm{26}}$Al, and $^{\textrm{41}}$Ca are measured at HZDR and $^{\textrm{53}}$Mn at ANU.

This contribution presents initial findings from the measurements of these radionuclides in a set of lunar regolith samples, discussing their role in determining the sample's exposure history. Additionally, we will provide insights into preliminary $^{\textrm{60}}$Fe data and updates on the quest for interstellar $^{\textrm{244}}$Pu.

Speaker: Sebastian Zwickel (Helmholtz-Zentrum Dresden-Rossendorf)

NPA_XI_PosterPitch_SZ.pdf

71 Mass measurements of neutron-rich nuclides at the N=126 shell with the FRS Ion Catcher

Direct evidence of the r-process has recently been observed in neutron star mergers, but the debate on the Nucleosynthesis environment is still far from over. Due to the scarcity of experimental information, modern r-process network calculations rely on theoretical models that give divergent predictions as one moves away from the valley of stability. Nuclear masses help to determine the r-process path and shed light on the Nucleosynthesis environment. Thus, high-precision mass measurements are performed to provide key input parameters to r-process calculations.

At GSI Darmstadt, experiments with exotic nuclides are performed, enabling the study of nuclei far from stability. These nuclei are produced at relativistic energies by projectile fragmentation or fission, separated in the fragment separator FRS and sent to the FRS Ion catcher (FRS-IC) for mass measurements utilizing its multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). An experiment was performed at the FRS-IC within FAIR Phase-0 close to the N=126 line, which is significant for nuclear structure and astrophysics studies and can help us better understand the r-process. Preliminary results from this experiment will be presented, including the first mass measurements of $^{204}Au$ and $^{205}Au$, where significant deviations from AME20 extrapolations indicate a change in the nuclear structure.

Speaker: Ms Kriti Mahajan (Justus-Liebig University, Giessen and HFHF Campus, Giessen)

156_286_Pitch.pdf

72 Neutron-capture in the wild: finding r-process enhanced metal-poor stars in the Milky Way and beyond

The lowest metallicity stars in the Milky Way Halo are the fossil records of the earliest star-forming environments in the universe. Their chemical abundance patterns help us understand primordial nucleosynthesis, the mass function of the first stars, and the pathways that led to the chemical complexity we observe today. However, there is still debate about when (and for how long) the universe transitioned from metal-free to the first chemical enrichment episodes that triggered low-mass star formation. In that context, metal-poor stars with enhancements in elements formed by the r-process can hold valuable clues to this intricate cosmic puzzle. Such stars are rare and difficult to find. In this presentation, I will talk about the serendipitous discovery and chemo-dynamical analysis of SPLUSJ1424, an old, low-mass, extremely metal-poor halo star enhanced in elements formed by the r-process. At [Fe/H]=-3.39, this is one of the lowest metallicity stars with measured Th and has the highest Th/Eu ratio observed to date, making it part of the "actinide-boost" category. Analysis suggests that the gas cloud from which SPLUSJ1424-2542 was formed must have been enriched by at least two progenitor populations, including a supernova explosion of metal-free stars and a neutron star merger event.

Speaker: Vinicius Placco (NSF NOIRlab)

158_288_Pitch.pdf

NPA_Poster_placco.pdf

73 $^{12}\mathrm{C}(\alpha,\gamma)^{16}\mathrm{O}$ cross section measurements with the ERNA separator

The amount of carbon and oxygen generated during the helium burning phase of stars has profound implications for stellar evolution. A primary source of this uncertainty lies in the $^{12}\mathrm{C}(\alpha,\gamma)^{16}\mathrm{O}$ reaction, which has been under investigation for over six decades. Despite persistent efforts, the uncertainty regarding the astrophysical factor remains above 10%, under which it would be possible to compare observations and models.

Direct measurements of the cross section within the Gamow window (approximately 0.3 MeV) are unfeasible due to its low value, necessitating reliance on R-Matrix extrapolations for estimation. To achieve a precise extrapolation, high-precision measurements targeting various aspects of the intricate reaction mechanism of $^{12}\mathrm{C}(\alpha,\gamma)^{16}\mathrm{O}$ are needed.
The current cross-section estimation in the Gamow window is strongly constrained by the data from the ERNA collaboration in the $E_\mathrm{CM}$ range of 1.9-4.9$\,\mathrm{MeV}$. The ERNA separator has undergone several upgrades to expand the measurement range and enhance the capability to distinguish between the contribution of $E_1$, $E_2$, and cascade transitions to the cross section.

The experimental apparatus is now fully operational for these measurements, and the campaign has started. This contribution provides an overview of the commissioning of the separator and presents preliminary results from the ongoing measurement campaign.

Speaker: Claudio Santonastaso (Università della Campania & INFN-Na)

PosterFlash.pdf

74 Search for Supernova-produced $^{60}$Fe in Antarctica Tracing the Local Interstellar Cloud

The presence of long-lived radionuclides provides insights into the solar system's history. The radionuclide $^{60}$Fe (t$_{1/2}\,$=$\,$2.6$\,$Myr) is mainly synthesized in massive stars and subsequently ejected by supernovae. Embedded into dust grains, $^{60}$Fe can enter the solar system and be deposited into terrestrial archives, where it evidences stellar explosions even after several million years.

Expanding upon the discovery of increased levels of $^{60}$Fe in million year old deep-ocean material and a recent influx into Antarctic snow, we now aim to investigate the influx pattern in the unexplored time interval 50$\,-\,$80$\,$kyr before present. A 300$\,$kg sample of the Antarctic EPICA Dronning Maud Land (EDML) ice core was selected to probe the recent $^{60}$Fe influx and implications for the formation of the Local Interstellar Cloud. Benefiting from their remoteness, Antarctic ice cores offer a unique geological archive with minimal terrestrial contamination.

The ultra-low deposition of a few $^{60}$Fe atoms per cm$^{2}$ per year can only be investigated by accelerator mass spectrometry. The DREAMS facility (HZDR) was used to measure the cosmogenic radionuclides $^{10}$Be, $^{26}$Al and $^{41}$Ca, whereas HIAF (ANU), as the sole capable facility worldwide, is required for measurements of $^{53}$Mn and $^{60}$Fe. We report on the recent results of this project.

Speaker: Annabel Rolofs (Helmholtz-Zentrum Dresden-Rossendorf)

NPAXI_Pitch_Rolofs.pdf

75 NG-Trap: System for Measuring Neutron Capture Cross-sections of Short-lived Fission Fragments

Almost all nuclei heavier than iron are produced through neutron capture nucleosynthesis, about half of them by the rapid (r) process. One of the limiting factors in understanding the r-process is the need for neutron capture cross-section measurements on unstable nuclei. As shown with the recent measurement of $^{88}$Zr (Shusterman et al., Nature 2019), neutron capture cross-sections can exhibit unpredictable behaviour.

We propose a novel method of measuring neutron capture cross-sections of short-lived nuclei. Neutron-rich nuclei produced via neutron-induced fission inside of a gas-filled stopping cell will form a mass-selected cooled low-energy beam, which will be transported into a linear Paul trap (coined ‘NG-Trap’), forming a target. This ‘cloud target’ of up to $10^{10}$ ions will then be irradiated with neutrons. The reaction products will then be identified and counted using a multiple-reflection time-of-flight mass-spectrometer (MR-TOF-MS), thus extracting the capture cross-sections.

This poster will present a breakthrough achievement towards the goal of generating the required ‘cloud target’. A demonstrator system with an ion capacity of more than $10^{10}$ ions will be presented. This system is a major milestone of the plan to install a high-capacity trap at the Soreq Applied Research Accelerator Facility (SARAF), currently under construction in Yavne, Israel.

Speaker: Heinrich Wilsenach (Justus-Liebig-Universität/Tel Aviv University)

HWilsenach_FlashSlide.pdf

76 Impact of ${}^{56}$Ni production in neutrino-driven winds from long-lived binary neutron star merger remnants

We investigate the nucleosynthesis and kilonova light curve based on recent long-term binary neutron star merger simulations that incorporate a two-moment neutrino-transport scheme. The ejecta are evolved for 30 days using axisymmetric radiation-hydrodynamics simulations coupled in-situ to a complete nuclear network. For the first time, we find that the neutrino-driven wind from the post-merger remnant is mostly proton-rich. The resulting nucleosynthesis products are predominantly ${}^{56}$Ni and other iron-group elements. After a few days, the decay of ${}^{56}$Ni and later ${}^{56}$Co becomes the primary source of heating in the expanding matter, which significantly alters the time dependence of the kilonova light curve. The observation of this effect would be a smoking gun for the presence of a long-lived neutron-star remnant in future kilonova observations.

Speaker: Maximilian Jacobi (University of Jena)

318_319_Pitch.pdf

77 Constraining the Astrophysical $\gamma$ Process: Cross Section Measurements of (p,$\gamma$) Reactions in Inverse Kinematics

Heavy element nucleosynthesis is largely governed by $n$-capture processes. However, a group of neutron-deficient isotopes, the $p$ nuclei, cannot be formed by any of those processes. These $\sim30$ nuclei are believed to be formed in the $\gamma$ process through a sequence of photodisintegration reactions on preexisting $r$- and $s$-process seeds. Reproducing the solar $p$-nuclei abundances using nuclear reaction networks requires input on a vast network of mostly radioactive isotopes. As experimental cross sections of $\gamma$-process reactions are almost entirely unknown, the related reaction rates are based on Hauser-Feshbach calculations and therefore carry large uncertainties. Therefore, it is crucial to develop techniques to measure these important reactions within the astrophysically relevant Gamow window with radioactive beams. The SuN group at FRIB has been developing such a program for the past decade.
This work focuses on two of the first measurements of $(\mathrm{p},\gamma)$ reactions in inverse kinematics with this setup, namely the ${}^{82}\mathrm{Kr}(\mathrm{p},\gamma){}^{83}\mathrm{Rb}$ with a stable beam, and the ${}^{73}\mathrm{As}(\mathrm{p},\gamma){}^{74}\mathrm{Se}$ reaction in our first radioactive beam experiment. Specifically, the latter reaction is found to be of significant importance to the final abundance of the lightest $p$-nucleus, ${}^{74}\mathrm{Se}$, as the inverse reaction ${}^{74}\mathrm{Se}(\gamma,\mathrm{p}){}^{73}\mathrm{As}$ is the main destruction mechanism of $^{74}\mathrm{Se}$.

Speaker: Artemis Tsantiri (Facility for Rare Isotope Beams / Michigan State University)

NPA_slide_Tsantiri.pdf

78 Variety of disk wind-driven explosions in massive rotating stars

At the end of its evolution, the collapse of a massive star's core into a proto-neutron star is the starting point for a complex sequence of events with many possible outcomes.
Specifically, very compact and rotating stars with a high mass ($M_*>16 \,M_\odot$), are likely to create a so-called ``failed core-collapse supernova'', forming a black hole surrounded by an accreting disk. It has been shown that the disk wind generated through viscous dissipation inside the disk may be the source of high energy ($E_\mathrm{expl}>10^{52}$ erg) supernovae with a high $^{56}$Ni mass (M$_{^{56}{Ni}}\ge 0.1\, M_\odot$).

In this scenario, the properties of the ejecta and the $^{56}$Ni production are strongly related to the wind injection from the accretion disk. In this talk, I will analyze these properties, investigating the impact of the disk mass and energy injected from the system on the final ejecta. I will focus on observational properties such as the explosion energy, the ejecta mass, and the $^{56}$Ni mass produced for different progenitor model. I will then show the strong correlation between the explosion energy and the ejecta mass, and compare our results for the $^{56}$Ni mass distribution with observational data.

Speaker: Ludovica Crosato Menegazzi (Max Planck Institute for Gravitational Physics)

093_253_Pitch.pdf

Poster Session

79 Emulator for the r-process and its energy generation in neutron-star merger remnants

The rapid neutron-capture process ($r$-process), known to operate in neutron-star merger (NSM) remnants, produces heavy elements whose radioactive decay deposits energy into the ejecta and powers a distinctive thermal glow called kilonova. However, an online implementation of the $r$-process in simulations is challenging due to the associated large number of isotopes in a full nuclear network. In this talk, we will present a machine learning method to emulate the $r$-process and its energy generation that can be efficiently incorporated in hydrodynamic simulations. We use this method to study the effects of $r$-process heating on the properties of NSM ejecta and kilonova.

Speaker: Zewei Xiong (GSI Helmholtzzentrum für Schwerionenforschung)

80 Alpha induced reactions on $^{124}$Xe for the astrophysical p-process

Majority of the heavy chemical elements are formed via neutron capture reactions. However, there are a few proton rich nuclei (p-isotopes) which cannot be created these ways.In a high temperature environment pre-existing nuclei can photodissociate, and through $(\gamma,\mathrm{n})$ reactions the p-isotopes can be created. Subsequent $(\gamma,\mathrm{n})$ reactions increase the neutron separation energy, and charged particle release in $(\gamma,\alpha)$ and $(\gamma,\mathrm{p})$ reactions become favourable, diverting the reaction flow towards lower masses.

Reaction network calculations using astrophysical and nuclear input parameters often fail to reproduce the abundances of naturally occurring p-isotopes. The input reaction rates are usually derived from the Hauser-Feshbach statistical model with considerable uncertainty. Benchmarking the model calculation is crucial for accurate predictions. Experimentally the cross section of the radiative capture is determined, and the photodisintegration rate is derived employing the detailed balance.

In this study, the cross section of $^{124}\mathrm{Xe}(\alpha,\gamma){}^{128}\mathrm{Ba}$ and ${}^{124}\mathrm{Xe}(\alpha,\mathrm{n}){}^{127}\mathrm{Ba}$ was measured by the activation technique using Atomki's cyclotron accelerator. The experiments were performed using a thin-window gas cell in the astrophysically relevant energy range $E_\alpha = 10-15 \,\mathrm{MeV}$. The $\gamma$-photons following the decay of the reaction products were detected with a high purity germanium detector.

Details of the experiment and preliminary results will be presented.

Speaker: Ákos Tóth (HUN-REN ATOMKI)

81 Experimental study of the ${}^{29}$Si(p,$\gamma$)${}^{30}$P reaction for classical nova nucleosynthesis

$^{29}$Si is believed to be produced during classical nova events. The measurements of the isotopic ratios in primitive meteorites can represent precisely the amount of $^{29}$Si produced by such events. However, there is no unambiguous evidence for the nova paternity of presolar stardust grains. Therefore, it is important to know precisely how much $^{29}$Si is produced in classical novae.

To do reliable theoretical calculations, we need to know the cross section of the $^{29}\mathrm{Si}(\mathrm{p},\gamma)^{30}\mathrm{P}$ reaction at astrophysically relevant energies. The direct capture (DC) cross section of $^{29}\mathrm{Si}(\mathrm{p},\gamma)^{30}\mathrm{P}$ has not been measured so far and for the strengths of some low energy resonances ambiguous data can be found in the literature. Therefore, the aim of the present work was the experimental study of this reaction. The strength of the $E_\mathrm{p}=416\,\mathrm{keV}$ resonance was measured as well as the DC cross section. For the measurements the proton beam was provided by the Tandetron accelerator of Atomki. The natural abundance of $^{29}$Si is about $4\%$, so enriched targets are necessary for the DC experiments. For resonance strength natural isotopic composition SiO$_{2}$ thick targets were used.

In this poster I present the details of the experimental procedure and some results.

Speaker: Zsolt Mátyus (HUN-REN Institute for Nuclear Research)

NPA-XI poster_5.pdf

82 Understanding 22Na cosmic abundance

We have developed a new, extremely precise experimental approach for measuring the lifetimes of excited states. This method uses gamma-tracking detectors with high resolution in energy and angle.

This method has been used at GANIL, France, to measure the lifetimes of 23Mg excited states. The gamma rays were measured with the AGATA gamma-ray detector, and the ejectiles from the 3He(24Mg,alpha)23Mg* reaction were measured in coincidence with the VAMOS++ spectrometer. This measurement was used to constrain the rate of the 22Na(p,gamma)23Mg reaction, and to determine the maximum detection distance of the 22Na produced in novae.

Ref: Fougères, Chloé, et al. "Search for 22Na in novae supported by a novel method for measuring femtosecond nuclear lifetimes." Nature communications 14.1 (2023): 4536.

Speaker: Francois de Oliveira Santos (GANIL)

83 Homogeneous analysis of 10 highly r-process enhanced stars

A small fraction of old, metal-poor stars exhibits significant enhancement in elements produced through the rapid neutron capture (r-) process, offering a unique laboratory to investigate this process. The R-Process Alliance's initial data release uncovered numerous highly r-processed (r-II) stars. In my work I delve into a detailed chemical analysis of ten such stars, utilizing high-quality spectra and examining over 2000 absorption lines spanning 330 to 940 nm across 49 chemical species. This meticulous examination yields the most comprehensive and uniformly analyzed collection of r-II stars to date. A systematic approach ensures reliable abundance distributions, facilitating the identification of potential variations in chemical compositions among the stars, indicative of r-process variability. The research aims to discern patterns, differentiate genuine abundance disparities from instances of r-process Universality, and utilize these findings to constrain r-process site and nucleosynthesis pathways. Two specific regions of elements are investigated: the region from Ru-Ag, where signatures of fission fragment deposition have recently been discovered by Ian Roederer and published in Science (Roederer, 2023), and the region of the third peak elements Os and Ir, which is still poorly explored in these stars.

Speaker: Mila Racca (Stockholm University)

146_Poster_Mila.pdf

84 $^{12}\mathrm{C}(\alpha,\gamma)^{16}\mathrm{O}$ cross section measurements with the ERNA separator

The amount of carbon and oxygen generated during the helium burning phase of stars has profound implications for stellar evolution. A primary source of this uncertainty lies in the $^{12}\mathrm{C}(\alpha,\gamma)^{16}\mathrm{O}$ reaction, which has been under investigation for over six decades. Despite persistent efforts, the uncertainty regarding the astrophysical factor remains above 10%, under which it would be possible to compare observations and models.

Direct measurements of the cross section within the Gamow window (approximately 0.3 MeV) are unfeasible due to its low value, necessitating reliance on R-Matrix extrapolations for estimation. To achieve a precise extrapolation, high-precision measurements targeting various aspects of the intricate reaction mechanism of $^{12}\mathrm{C}(\alpha,\gamma)^{16}\mathrm{O}$ are needed.
The current cross-section estimation in the Gamow window is strongly constrained by the data from the ERNA collaboration in the $E_\mathrm{CM}$ range of 1.9-4.9$\,\mathrm{MeV}$. The ERNA separator has undergone several upgrades to expand the measurement range and enhance the capability to distinguish between the contribution of $E_1$, $E_2$, and cascade transitions to the cross section.

The experimental apparatus is now fully operational for these measurements, and the campaign has started. This contribution provides an overview of the commissioning of the separator and presents preliminary results from the ongoing measurement campaign.

Speaker: Claudio Santonastaso (Università della Campania & INFN-Na)

85 321D modelling of the interplay between turbulence and nuclear reactions in massive stars

Given the key role massive stars and core-collapse supernovae play in the Universe, developing theoretical models of massive stars and their final collapse is critical. Massive stars are complex 3D objects involving a wide range of interesting physical processes like convection. Stellar models would thus ideally be three-dimensional (3D) (magneto-)hydrodynamic models that include all the relevant physics. These 3D hydrodynamic models, however, must use time steps that are many orders of magnitude shorter than the lifetime of stars. This explains why most stellar evolution models are limited to 1D (e.g. GENEC, MESA codes), equivalent to limiting models to spherical symmetry (or averages). These 1D models have wide ranging applications in astrophysics due to the importance of massive stars. The predictive power of 1D models, however, is crippled by 1D prescriptions of 3D phenomena containing free parameters that need to be calibrated using observations. In this talk, I will present our recent efforts to study convection and its interplay with nuclear reactions in 3D. I will in particular focus on cases where deviations from spherical symmetry are expected (e.g. shell mergers) and discuss how these 3D simulations can be used to improve 1D models.

Speaker: Raphael Hirschi (Keele University)

Hirschi_NPA_2024.pdf

86 A new grid of 3D non-LTE Barium abundance corrections

We present a new grid of 3D non-LTE -- 1D LTE Barium abundance corrections developed in the framework of the EU-funded ChETEC-INFRA project. The grid covers dwarfs, subgiant, and giant stars of spectral type F, G, K from solar to metal-poor metalicities for five commonly used Ba II lines. Based on a total of about 100 CO5BOLD 3D hydrodynamical stellar atmosphere models and associated 1D MARCS models, the non-LTE level population departure coefficients of an updated barium model atom (Gallagher 2020) were computed with the state-of-the-art 1D statistical equilibrium code Multi (Carlsson 1986) for a set of Ba abundances covering the observed range. In a second step, 3D non-LTE synthetic spectra were computed with the Linfor3D code. Comparison with the 1D LTE equivalent widths allows us to derive the desired abundance corrections, providing a simple means of improving the accuracy of the barium abundance obtained from standard 1D LTE analyses of stellar spectra.

We discuss the relevance of the corrections across the Hertzsprung-Russell
diagram, depending on the spectral line and Ba abundance, and demonstrate that the 3D non-LTE corrections for Ba II are significantly different from the more commonly used 1D NLTE — 1D LTE abundance corrections.

Web page: https://www.chetec-infra.eu/3dnlte/

Speaker: Matthias Steffen (Leibniz Institute for Astrophysics Potsdam)

Ba_grid_poster.pdf

87 A novel numerical library for neutrino-matter interaction rates in binary neutron star mergers

GW170817 marked the first outstanding detection of a gravitational-wave signal generated by the coalescence of a binary neutron star (BNS) system. The successful follow-up campaign carried out by electromagnetic facilities has confirmed the remarkable scientific potential of such events in the context of newborn multimessenger astrophysics. In this respect, reliable theoretical modeling of the coalescence is crucial to avoid systematic errors when interpreting observations. Among the important physical effects to be considered, the interplay between neutrinos and nuclear matter can generate distinct fingerprints on the coalescence, such as affecting the stability of the remnant in the merger aftermath or defining the initial conditions from which the rapid neutron capture process in the ejecta takes on.

To this end, we present “bns_nurates”, a novel numerical library written to compute neutrino-matter interaction rates in BNS context. “bns_nurates” is designed to account for different kinds of nuclear physics effects on the interaction rates. As an example of application, we compare the importance of different reaction rates for typical conditions realized during the post-merger phase. Such a study can help to select which relevant reactions need to be included to correctly predict the impact of neutrinos on the system.

Speaker: Leonardo Chiesa (University of Trento)

NPA_XI_poster_Leonardo_Chiesa_#32_indico.pdf

88 An atomic approach to the opacity of open-shell ions

The opacity of plasma is often utilized in astrophysics for studying solar models, (solar) neutrino observations or neutron star mergers. The opacity of an atomic ion hereby quantifies how photons are absorbed or re-scattered by the plasma ions. The opacity of different ion sources also enters explicitly the radiation transport in different environments, such as stellar interiors, fusion devices or short-wavelength plasma light sources, at least, if local thermodynamic equilibrium (LTE) conditions can be assumed.

To better understand the sensitivity and role of (different) opacities in modelling the light curves from kilonovae, the Jena Atomic Calculator (JAC) has been expanded in order to compute, analyze and discuss different kinds of opacity. JAC [1] is based on Julia, a new programming language for scientific computing, which provides an easy-to-use but powerful platform to extent atomic theory towards new (astrophysical) applications for almost all atoms and ions across the periodic table, including atomic cascade processes of different sort and complexity [2].

[1] S. Fritzsche, Comp. Phys. Commun. 240, 1 (2019); https://github.com/OpenJAC/JAC.jl
[2] S. Fritzsche, P. Palmeri & S. Schippers, Symmetry 13, 520 (2021).

Speaker: Stephan Fritzsche (HI-Jena)

89 Bayesian study of quasi-universal relations for neutron stars normal modes

Gravitational wave asteroseismology is a promising approach for studying neutron stars' characteristics and constraining dense matter equation of state (EoS).  Several quasi-universal empirical relations have been developed to link the frequencies of normal modes to various stellar properties such as mass and radius. These relations allow us to extract macroscopic information about the stars from a detected signal. However, their universality is typically tested using a small number of distinct nuclear models.

We use Bayesian inference employing the so-called meta-modeling technique to investigate a large set of equations of state that are compatible with astrophysical constraints, nuclear-physics experimental data, and current theoretical estimates from chiral effective field theory. To this aim, we employ a Markov chain Monte Carlo algorithm for the sampling of the posterior with high statistics. The modes are, then, evaluated using the Cowling approximations for all the equations of state making possible to test the universality for a large set of EoS compatible with the aforementioned constraints.

Speaker: Gabriele Montefusco (CNRS)

90 CERES survey: chemical abundances of neutron capture elements up to Eu

The rapid neutron capture process is responsible for the synthesis of roughly half of the elements heavier than Zn ($Z>30$) in the solar system, however, it is still unclear what the exact astrophysical sites of the r-process are, and if different r-process nucleosynthetic channels exist, particularly at low metallicities. Metal-poor stars play a key role in understanding the nucleosynthesis of heavy elements in the early Universe, as their chemical abundances reflects the composition of the gas in which they formed. These stars show a variety of heavy chemical abundances patterns, with extreme variation in the r-process elements, from $[\mathrm{Eu}/\mathrm{Fe}]$ below solar to $[\mathrm{Eu}/\mathrm{Fe}]>1$ in r-rich stars. This large scatter in heavy elements abundances seems to suggest that more than one formation site is responsible for the nucleosynthesis of these elements, and that the formation happens under different physical conditions.

In this talk I will present the new abundance results of heavy neutron capture elements, including the poorly studied Ru and Ag, for a sample of 52 very metal-poor stars ($[\mathrm{Fe}/\mathrm{H}]<-1.5$). The talk will be focused on exploring the impact of the r-process at low metallicities, by comparing the observed chemical abundances with those predicted by theoretical models.

Speaker: Linda Lombardo (Goethe University Frankfurt)

EPJA3_IMG_3556.JPG

EPJA3_LindaLombardo_IMG_3438.JPG

91 Commissioning of a New, Innovative Gas Target for Nuclear Astrophysics

We present a newly developed jet and extended windowless gas target system, tailored to meet the precision measurement demands of modern nuclear astrophysics. Our system can be operated either in jet or extended modes without necessitating modifications in pumping power. Real-time monitoring of a jet, facilitated by laser interferometry techniques, ensures control of target parameters during operation. Our development process involved comprehensive computational fluid dynamics simulations to optimize nozzle geometry.
Characterization of the jet target involved both absolute target thickness determination using alpha energy loss techniques and relative thickness measurements via laser interferometry. These techniques collectively ensure a comprehensive understanding and control of target parameters. Experimentally measured the areal density of the jet on the order of atoms/cm.
For the extended gas target setup, pressure, and temperature profiles are measured to construct the density profile of an extended gas target. Additionally, a beam calorimeter has been developed and tested to measure the beam intensity.
The setup has undergone development and testing at the Rossendorf Center and now is in the commissioning phase at the Felsenkeller underground ion accelerator laboratory. Our report will provide insight into the developments, characterization, and operational capabilities of our newly developed combined gas target system.

Speaker: Konrad Schmidt (HZDR)

92 Comparing Radiative Transfer Methods for Kilonovae

The electromagnetic signals from the kilonova AT2017gfo provide an opportunity to study an astrophysical site of the r-process which produced about half of all nuclei heavier than iron. In order to be able to connect kilonova light curve and spectral properties to the ejecta dynamics it is important to address the role of the individual simplifying assumptions commonly used in theoretical modelling. Fully self-consistent radiative transfer Monte Carlo simulations are nowadays possible. However, due to computational limitations and the need to cover a large parameter space it is important to develop fast and accurate modelling pipelines.

We compare two different methods for simulating kilonova light curves based on two-dimensional simulations of the ejecta dynamics: Monte Carlo radiative transfer (ARTIS code) and a two-moment scheme adopting the M1 approximation (ALCAR code). By this, we are able to benchmark the computationally cheap ALCAR code against the more expensive ARTIS code. Furthermore, we benchmark commonly used approximations for the thermalization of radiative decay products against fully microscopic and local description of the energy deposition.

This work is supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (ERC Advanced Grant KILONOVA No. 885281).

Speaker: Gerrit Leck (GSI Helmholtzzentrum für Schwerionenforschung GmbH)

93 Complete r-Process Survey

The production of heavy elements by the rapid neutron capture process (r-process) can occur in neutron star mergers and probably in supernovae driven by strong magnetic fields. We use a complementary method to using trajectories from simulations and explore a complete and extended range of astrophysical conditions with a parametric model. This allows us to investigate all possible conditions for the r-process, also beyond current simulations. Final abundances are in good agreement with those of Lagrangian tracer particles from simulations. Therefore, our survey can be used to compare to observations and investigate the impact of the nuclear physics input.

Speaker: Jan Kuske (TU Darmstadt)

JanKuskeNPAPoster.pdf

94 Constraining the ${}^{69}$Zn Neutron Capture Cross-Section via the Beta-Oslo Method

The existence of the weak intermediate neutron-capture process (i-process) explains the observed astrophysical abundances of elements around the $Z<50$ region. Neutron capture reactions in the $A=70$ mass region for Ni, Cu, and Zn isotopes are known to produce large variations in predicted i-process abundances. Predicted stellar abundances of Ga are particularly affected by the $^{69}\mathrm{Zn}(\mathrm{n},\gamma){}^{70}\mathrm{Zn}$ reaction. The $\beta$-decay of ${}^{70}\mathrm{Cu}$ offers an unique opportunity to utilize the $\beta$-Oslo method to experimentally determine the $\gamma$-ray strength function and nuclear level density and constrain the ${}^{69}\mathrm{Zn}(\mathrm{n},\gamma){}^{70}\mathrm{Zn}$ reaction rate for i-process nucleosynthesis. ${}^{70}\mathrm{Cu}$ has three different $\beta$-decaying spin-parity states that populate different spin ranges at similar excitation energies in the daughter nucleus: the $6^-$ ground state, the $101\,\mathrm{keV}$ $3^-$ isomeric state, and the $242\,\mathrm{keV}$ $1^+$ isomeric state. In experiments performed at the NSCL and FRIB, the isomers and ground state of $^{70}\mathrm{Cu}$ were produced and delivered to the Low Energy Beam and Ion Trap (LEBIT) and then to Summing NaI (SuN) Total Absorption Spectrometer. Preliminary results from $\beta$-Oslo analysis will be presented along with the preliminary constrained ${}^{69}\mathrm{Zn}(\mathrm{n},\gamma){}^{70}\mathrm{Zn}$ cross-section. Initial results from the commissioning of the SuN upgrade (to SuN++) will also be presented.

Speaker: Eleanor Ronning (Michigan State University/FRIB)

052_Poster_Ronning.pdf

95 Constraining the Astrophysical $\gamma$ Process: Cross Section Measurements of (p,$\gamma$) Reactions in Inverse Kinematics

Heavy element nucleosynthesis is largely governed by $n$-capture processes. However, a group of neutron-deficient isotopes, the $p$ nuclei, cannot be formed by any of those processes. These $\sim30$ nuclei are believed to be formed in the $\gamma$ process through a sequence of photodisintegration reactions on preexisting $r$- and $s$-process seeds. Reproducing the solar $p$-nuclei abundances using nuclear reaction networks requires input on a vast network of mostly radioactive isotopes. As experimental cross sections of $\gamma$-process reactions are almost entirely unknown, the related reaction rates are based on Hauser-Feshbach calculations and therefore carry large uncertainties. Therefore, it is crucial to develop techniques to measure these important reactions within the astrophysically relevant Gamow window with radioactive beams. The SuN group at FRIB has been developing such a program for the past decade.
This work focuses on two of the first measurements of $(\mathrm{p},\gamma)$ reactions in inverse kinematics with this setup, namely the ${}^{82}\mathrm{Kr}(\mathrm{p},\gamma){}^{83}\mathrm{Rb}$ with a stable beam, and the ${}^{73}\mathrm{As}(\mathrm{p},\gamma){}^{74}\mathrm{Se}$ reaction in our first radioactive beam experiment. Specifically, the latter reaction is found to be of significant importance to the final abundance of the lightest $p$-nucleus, ${}^{74}\mathrm{Se}$, as the inverse reaction ${}^{74}\mathrm{Se}(\gamma,\mathrm{p}){}^{73}\mathrm{As}$ is the main destruction mechanism of $^{74}\mathrm{Se}$.

Speaker: Artemis Tsantiri (Facility for Rare Isotope Beams / Michigan State University)

NPAXI_Poster_Tsantiri.pdf

96 Constraining the NiCu cycle in X-ray bursts: Spectroscopy of ${}^{60}$Zn

Type-I X-ray bursts are thermonuclear explosions in the atmospheres of accreting neutron stars in close binary systems. During these bursts, temperatures are achieved ($0.8-1.5\,\mathrm{GK}$) such that breakout from the HCNO cycle occurs, resulting in a whole new set of thermonuclear reactions; the rp-process.

Sensitivity studies have highlighted the ${}^{59}\mathrm{Cu}(p,\gamma){}^{60}\mathrm{Zn}$ reaction as significant in its impact along the rp-process path. In particular, competition between the ${}^{59}\mathrm{Cu}(p,\alpha){}^{56}\mathrm{Ni}$ and ${}^{59}\mathrm{Cu}(p,\gamma){}^{60}\mathrm{Zn}$ reactions within the NiCu cycle determines whether nucleosynthesis flows towards higher-mass regions. At present, stellar reaction rates for both of these processes are based entirely on statistical-model calculations.

Recently, however, an indirect study of the nucleus $^{60}\mathrm{Zn}$ has surprisingly shown a plateau in the level-density of states in the region of interest, contrary to the usual expectation of exponential growth with increasing excitation energy. As a result, a statistical-model approach of the ${}^{59}\mathrm{Cu}(p,\gamma)$ reaction rate may be insufficient, and it is therefore now essential to explore the properties of excited states in $^{60}\mathrm{Zn}$ that influence the astrophysical ${}^{59}\mathrm{Cu}(p,\gamma){}^{60}\mathrm{Zn}$ reaction.

In this work, we aim to utilise the ${}^{59}\mathrm{Cu}(d,n)$ reaction in inverse kinematics at the Facility for Rare Isotope Beams (FRIB) to obtain the first measurement of resonances in the ${}^{59}\mathrm{Cu}(p,\gamma)$ reaction.

Speaker: Connor O'Shea (University Of Surrey)

056_Poster_OShea.pdf

97 Contribution of individual astrophysical events to chemical evolution of dwarf galaxies

Stars of different properties produce different elements. For instance, rotating massive stars are supposed to produce trans-iron elements at low metallicities (e.g. Frischknecht et al. 2012, Limongi & Chieffi 2018). Also, in low-mass galaxies, astrophysical events can appear sporadically. Thus, the relative contribution of astrophysical events to the chemical enrichment may not be compared to that in the solar neighbourhood.

Dwarf galaxies provide insights into the chemical enrichment in low-mass and low-metallicity systems. According to the cosmological model, massive galaxies are formed through mergers of less massive galaxies. When a dwarf galaxy is formed from lower-mass galaxies, individual events influence abundances ratios of each building-block galaxy, and the impact may be reflected in the ratios of the merged galaxy.

We investigate the contribution of individual events to the chemical enrichment of a dwarf galaxy in a context of hierarchical galaxy formation. The chemical evolution of building-block galaxies is derived with a numerical model where the stochasticity is introduced into the occurrence of astrophysical events. We discuss that the contribution of r-process events to the chemical enrichment may be large at low metallicities and that rotating massive stars can create part of the dispersion in abundance ratios through the weak s-process.

Speaker: Nao Fukagawa (National Astronomical Observatory of Japan)

Poster_NPA-XI_NFukagawa_16sep2024.pdf

98 Core-collapse supernova yields in galactic chemical evolution

The amount and composition of matter ejected in core-collapse supernovae (CCSNe) are key uncertainties in models of galactic chemical evolution (GCE). Extensive grids of stellar models with varying mass and metallicity are needed. Although 3D simulations of stellar evolution and CCSNe have recently become available, the large computational cost only allows large sets of simulations under the assumption of spherical symmetry. In this study, we simulate the collapse and explosion of 67 massive stars with zero-age main sequence masses between 11 and 75 solar masses and three different metallicities. Our CCSN simulations include a self-consistent treatment of the proto-neutron star with a naturally evolving mass cut between remnant and ejecta. We provide nucleosynthesis results from an in-situ nuclear reaction network and use them as input for a GCE model of the Milky Way. This self-consistent chain allows for the exploration of uncertainties and comparison of the results to observations. With this study, we want to encourage the communities of stellar evolution and supernova simulations to use the latest advances in the respective fields to provide information useful for GCE models.

Speaker: Finia Jost (Technical University Darmstadt)

EPJA1_FiniaJost_IMG_3452.JPG

EPJA1_IMG_3547.JPG

Poster_NPA_id55.pdf

Slide_NPA_id55.pdf

99 Cosmogenic and Interstellar Radionuclides in Lunar Soil

The astrophysical site of the r-process remains an open question in nuclear astrophysics. Pure r-process radionuclides present in the solar system today that cannot originate from primordial events due to their comparably short half-lives (e.g. $^{\textrm{244}}$Pu t$_{1/2}\,\sim\,$81$\,$Myr) act as fingerprints of recent r-process events in the solar neighbourhood. The discovery of live $^{\textrm{244}}$Pu via single-atom counting with accelerator mass spectrometry (AMS) in deep-sea ferromanganese crusts has recently confirmed such r-process activity. We now aim to extend our search for interstellar $^{\textrm{244}}$Pu and also supernova-produced $^{\textrm{60}}$Fe (t$_{1/2}\,$=$\,$2.6$\,$Myr) to a different archive, lunar soil, which allows to map out the interstellar influx up to hundreds of millions of years ago. The proper characterization of the soil's exposure history and composition is important here. Alongside various analytical methods we measure cosmogenic radionuclides with half-lives in the order of million years via AMS. $^{\textrm{10}}$Be, $^{\textrm{26}}$Al, and $^{\textrm{41}}$Ca are measured at HZDR and $^{\textrm{53}}$Mn at ANU.

This contribution presents initial findings from the measurements of these radionuclides in a set of lunar regolith samples, discussing their role in determining the sample's exposure history. Additionally, we will provide insights into preliminary $^{\textrm{60}}$Fe data and updates on the quest for interstellar $^{\textrm{244}}$Pu.

Speaker: Sebastian Zwickel (Helmholtz-Zentrum Dresden-Rossendorf)

NPA_XI_Poster_SZ.pdf

100 Development of the Charge-Exchange Oslo Method and Application Towards Constraining Reaction Rates for Nucleosynthesis of Cosmochronometer ${}^{92}\mathrm{Nb}$

Charge-Exchange (CE) reactions are an important tool for studying the spin-isopin response of nuclei. They can be utilized to obtain information about interactions mediated by the weak nuclear force, such as $\beta$ and electron capture decay. Using the proportionality between Gamow-Teller strength (B(GT)) and the CE differential cross section, B(GT) distributions can be extracted indirectly. Since CE reactions are not limited to a narrow $Q$ value window, they provide information that is complementary to information obtained from $\beta$ and electron capture decay. Such data are necessary for constraining reaction rates that happen in dense and hot astrophysical environments. In the near future, it is planned to combine measurements in which GT strengths are extracted with $\gamma$-decay measurements, utilizing the Oslo method to extract level densities and $\gamma$-ray strength functions, which are also important for constraining astrophysical reaction rates. It is proposed to measure the ${}^{92}\mathrm{Zr}({}^{3}\mathrm{He},\mathrm{t}+\gamma)$ reactions at $420\,\mathrm{MeV}$ in RCNP to develop the Charge-Exchange Oslo (CE-Oslo) method and to extract reaction rates for the nucleosynthesis of cosmochronometer ${}^{92}\mathrm{Nb}$. This high precision study will lay a solid foundation for using the CE-Oslo method in future $(\mathrm{p},\mathrm{n}+\gamma)$ experiments in inverse kinematics with rare isotopes and make it possible to simultaneously extract nuclear level densities (NLDs), $\gamma$-ray strength functions ($\gamma\mathrm{SFs}$), $\beta$-decay strengths and ($\beta$-delayed) neutron decay probabilities ($P_\mathrm{n}$) on neutron-rich unstable nuclei, which are important for several nucleosynthesis processes, including the r, i, $\gamma$, and $\nu$ processes. The high resolution available for $({}^{3}\mathrm{He},\mathrm{t})$ experiments at RCNP will make it possible to extract level densities in two independent manners: by using the Oslo technique and by using the fine-structure analysis. From the measurement on ${}^{92}\mathrm{Zr}$, it will be possible to extract level densities and $\gamma$-ray strength functions which are relevant for the $\gamma$-process in type Ia supernovae and Gamow-Teller strength distributions of relevance for the $\nu$-process in core-collapse supernovae. These astrophysical phenomena are the possible sites for the production of long-lived ${}^{92}\mathrm{Nb}$, which can serve as a cosmochronometer. As an initial test, the CE-Oslo method is being tested on $(\mathrm{t},{}^{3}\mathrm{He}+\gamma)$ data taken previously with the S800 spectrometer in coincidence with the GRETINA $\gamma$-ray detector at FRIB. Preliminary results of the analysis will be shown at the conference.

This research is supported by the US National Science foundation, Grant No. 2209429, "Nuclear Astrophysics at FRIB".

References:
1. R. Zegers, Research Proposal, Submitted to the B-PAC at RCNP (2020)
2. T. Hayakawa et al., Ap.J.Lett. 779, L9 (2013)
3. A. Spyrou et al., Phys. Rev. Lett. 113, 232502 (2014)
4. B. Gao et al., Phys. Rev. C 101, 014308 (2020)

Speaker: Neshad D. Pathirana (Department of Physics and Astronomy, Michigan State University; Facility for Rare Isotope Beams (FRIB), Michigan State University; JINA-CEE)

202-Neshad-one_min_slide.pdf

202-Neshad-Poster.pdf

101 Differences in chemical enrichment of metal-poor Milky Way stars

The relative variations of the chemical compositions between metal-poor stars ($[\mathrm{F}/\mathrm{H}] < -1$) give the possibility to reveal the pure signature of unique nucleosynthesis processes. The study of the r-process is for instance one of the main goals of stellar archaeology.
In this work we present the atmospheric parameter, the main dynamic properties and the abundances of four metal-poor stars: HE 1523–0901, HD 6268, HD 121135, and HD 195636 ($-1.5 > [\mathrm{Fe}/\mathrm{H}] > -3.0]$).The abundances are derived from spectra obtained with the HRS echelle spectrograph at the Southern African Large Telescope, using both LTE and NLTE approaches, with an average error between $0.10$ and $0.20\,\mathrm{dex}$. The most metal-poor stars in our sample, HE 1523–0901, HD 6268 and HD 195636, show anomalies that are better explained by supernova models from fast-rotating stellar progenitors. If we consider the elements beyond Fe, HE 1523-0901 can be classifed as an r-II star, HD 6268 an r-I candidate, and HD 195636 and HD 121135 show a borderline r-process enrichment between limited-r and r-I star. Significant differences are observed between the r-process signatures in these stars. We discuss those in the light of the current understanding of r-process nucleosynthesis.

Speaker: Tamara Mishenina (Astronomical Observatory Odesa National University Ukraine)

025_Poster_Mishenina.pdf

102 Dipole strength in the well-deformed nucleus ${}^{154}$Sm in the Pygmy Resonance energy-region via $(\gamma,\gamma^\prime)$ reactions

The E1 $\gamma$-ray strengh of the Pygmy Dipole Resonance (PDR), close to the neutron threshold on the top of the low-energy tail of the Isovector Giant Dipole Resonance (IVGDR), exhausting only few percent of the TRK sum rule is known to affect significantly the radiative neutron capture cross section calculations of the astrophysical r-process [1] which is responsible for the nucleosynthesis of heavy neutron-rich nuclei in the universe.

So far, the PDR strength distribution has been measured in several neutron-rich nuclei [2,3], mostly on or near neutron shell closures, where the shape is (quasi) spherical. The systematic summed strengths in an isotopic and isotonic chains of the nuclear chart, seems to be linked to the neutron excess.

Although described in various microscopic and hydrodynamic theoretical models as oscillations of the neutron excess against an isospin neutral core, the nuclear structure (collective and/or singular character) of the PDR states and the strength fragmentation are still controverse.

The corresponding neutron-skin size, related to the (a)symmetry energy term is an important ingredient for the equation of state modeling the neutron stars.

Since the rised interest of the PDR strength as well from astrophysical as nuclear structure point of view and in order to complement our experimental database, one need to explore the case of deformed shapes where such information is limited to only a very few cases, as for ${}^{156}$Gd [4] and ${}^{164}$Dy [5]. In this talk, I will present our recent results on the well-deformed ${}^{154}$Sm ($\beta=0.34$) which we investigated via the ${}^{154}$Sm$(\gamma,\gamma^\prime)$ reactions up to the neutron-separation threshold $S_n = 7.97\,\mathrm{MeV}$, using the bremsstrahlung facility [6] at ELBE supra-conductor accelerator of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Germany, producing an electron beam of energy of $9.5\,\mathrm{MeV}$. An evidence for PDR strength have been observed which will be compared to the spherical isotope ${}^{144}$Sm at $N=82$ closed neutron shell and to the ${}^{156}$Gd isotone.

[1] S. Goriely, et al., Nucl. Phys. A 739 (2004) 331.
[2] D. Savran, et al., Prog. Part. Nucl. Phys. 70 (2013) 210.
[3] A. Bracco, et al., Eur. Phys. J. A 55 (2019) 233.
[4] M. Tamkas et al., Nuclear Physics A 987 (2019) 79
[5] O. Papst et al., Phys. Rev. C 87, 102, (2020) 034323
[6] R. Schwengner et al., Nucl. Instrum. Methods A 555 (2005) 211

Speaker: Dr Nadia Benouaret (University of Science and Technology Houari Boumediene (USTHB))

103 Early onset of color-superconducting quark matter in neutron stars

We present a relativistic density functional approach to color superconducting quark matter that mimics quark confinement by a fast growth of the quasiparticle self-energy in the confining region. The approach is shown to be equivalent to a chiral model of quark matter with medium dependent couplings. The approach to the conformal limit at asymptotically high densities is provided by a medium dependence of the vector-isoscalar, vector-isovector and diquark couplings motivated by non-perturbative gluon exchange [2]. While the (pseudo)scalar, vector-isoscalar and vector-isovector sectors of the model are fitted to the mesonic mass spectrum and vacuum phenomenology of QCD, the strength of interaction in the diquark channel is varied in order to obtain the best agreement with the observational constraints from measurements of mass, radius and tidal deformability of neutron stars. These constraints favor an early onset of deconfinement and color superconductivity in neutron stars with masses below one solar mass. We also discuss a new two-zone interpolation scheme for the construction of the hadron-to-quark matter transition [3] that allows to test different structures of the QCD phase diagram with one, two or no critical endpoints in simulations of supernova explosions, neutron star mergers and heavy-ion collisions. I argue that the formation of color-superconducting quark matter drives the trajectories of its evolution in supernovae and neutron star mergers towards the regimes reached in terrestrial experiments with relativistic heavy ion collisions.

[1] O. Ivanytskyi and D. Blaschke, Phys. Rev. D 105, 114042 (2022)
[2] O. Ivanytskyi and D. Blaschke, Particles 5, 514 (2022)
[3] O. Ivanytskyi and D. Blaschke, Eur. Phys. J A. 58, 152 (2022

Speaker: Oleksii Ivanytskyi (University of Wroclaw)

104 Experimental cross section of the $^3$He($\alpha$,$\gamma$)$^7$Be reaction around $E_\mathrm{cm}=3\,\mathrm{MeV}$

The ${}^3\mathrm{He}(\alpha,\gamma){}^7\mathrm{Be}$ reaction plays a major role both in the big bang nucleosynthesis (BBN) where it affects the primordial $^7$Li production, and in the solar energy generation via the pp-chain where as a branching point it affects the flux of neutrinos. Precise understanding of the reaction mechanism is of crucial importance for BBN and solar model calculations.

In case of the energy range relevant in the BBN, there are few experimental datasets, however in the solar relevant energy range it is impossible to measure experimental cross sections. For the solar models, one has to rely on extrapolation from higher energy datasets.
To aid these extrapolations, in the present study the reaction cross section was measured in the energy range covered so far with only one experimental dataset. The well known activation technique was employed, using a thin-window gas cell target containing $^3$He gas. The irradiations were performed by the cyclotron accelerator of Atomki. The $\gamma$-photons following the decay of the reaction products were detected with high purity germanium detector.

Details of the experiment and preliminary results will be presented along with a literature overview of the reaction and future plans to pinpoint crucial unknowns regarding this important reaction.

Speaker: Dr Tamás Szücs (Institute for Nuclear Research (Atomki))

202409 - NPA11 - 3He_ag.pdf

105 Experimental studies on the optical spectrum of the heavy r-process nuclide Cf-254 and its neighbors

The spontaneously fissioning isotope californium-254 is predicted to have a high impact on the brightness of electromagnetic transients associated with neutron star mergers on the timescale of 10 to 250 days, due to its 60-day half-life. [Zhu et al., AJL 863, L23 (2018)]. Experimental information on Cf-254 is scarce, owing to limited production capabilities in the laboratory. We have performed laser spectroscopy on this and neighboring isotopes at the RISIKO mass separator at Johannes Gutenberg University Mainz (JGU), Germany. For this, Cm targets were neutron-irradiated at Oak Ridge National Laboratory (ORNL), TN, USA, to breed Es-253,254. After the chemical separation at ORNL the Es fraction, which also contained some Cf-252, was shipped to JGU, via Florida State University, FL, USA, and then sent to Institut Laue-Langevin, Grenoble, France, for a second irradiation to produce more neutron-rich isotopes including, Cf-253 and Cf-254. The hyperfine structure of the $420\,\mathrm{nm}$ ground-state transition in Cf-253 and the isotope shift of Cf-254 in the $417\,\mathrm{nm}$ and $420\,\mathrm{nm}$ ground-state transitions were determined with high resolution down to $140\,\mathrm{MHz}$. These data provide a basis for a King plot analysis of the optical spectrum of Cf-254 based on known data of lighter californium isotopes.

Speaker: Mr Sebastian Berndt (Johannes Gutenberg Universität Mainz, 55099 Mainz, Germany)

106 Experiments with fast neutrons at nELBE

The neutron time-of-flight facility nELBE at Helmholtz-Zentrum Dresden-Rossendorf features the first photo-neutron source at a superconducting electron accelerator. The electrons are focused onto a liquid-lead target to produce bremsstrahlung which in turn produces neutrons via photo-nuclear reactions. The emitted neutron spectrum ranges from about 10 keV up to 15 MeV with a source strength of above $10^{11}$ neutrons per second. The very precise time structure of the accelerator with a bunch width of a few ps enables time-of-flight measurements at very short flight path.
The high repetition rate of 100 to 400 kHz in combination with the low instantaneous flux and the absence of any moderating materials provide favorable background conditions.
The very flexible beam properties at nELBE enable a broad range of nuclear physics experiments. Examples for the versatility of nELBE will be presented: From transmission measurements and inelastic neutron scattering and fission experiments to determine nuclear reaction cross sections with relevance for fundamental nuclear physics, reactor safety calculations, nuclear transmutation or particle therapy to experiments to investigate the response of novel particle detectors e.g. for dark matter search experiments, nuclear instrumentation or the range verification in cancer treatment.

Speaker: Roland Beyer (Helmholtz-Zentrum Dresden-Rossendorf)

107 Exploring late stages of massive stars evolution in the context of new precise nuclear reaction rates

In recent years, new experimental determinations of nuclear reaction rates relevant to astrophysics have been obtained using experimental (direct and indirect) and theoretical methods, highlighting specific trends such as the unexpected fusion hindrance phenomenon for ions or multiple resonances. Especially, a precise determination of the nuclear reaction rates is a crucial ingredient in understanding stellar evolution using stellar evolution models. We now need to take into account these new results, which can provide one of the keys to a better understanding of stellar and chemical evolutions.

New direct measurements of the $^{12}$C+$^{12}$C nuclear reaction at very low energies have been obtained by the STELLA collaboration in France, paving the way for improvements in stellar evolution modelling. Using the evolution code GENEC, we computed a grid of models (8-30 M$_{\odot}$) including rotation. We show the change of nuclear rates impacts the core properties, burning lifetime and nucleosynthesis. We highlight an enhanced effect due to rotation and a strong dependence on the stellar mass related to the observed resonance (Dumont 2024, revised). Finally, we will discuss the potential hindrance effects for the $^{12}$C+$^{16}$O and $^{16}$O+$^{16}$O nuclear reactions involved in later evolutionary stages, which will be measured as part of the CarbOx project.

Speaker: Thibaut Dumont (University of Strasbourg - IPHC)

108 Exploring nucleosynthetic processes in a large sample of Barium stars

Barium (Ba) stars belong to binary systems where a former asymptotic giant branch (AGB, now a white dwarf) star polluted the less evolved companion, which became enriched with material produced through the slow neutron capture process (s process). The currently observed Ba star preserves the abundance pattern of the AGB, allowing us to test the imprints of the s process. Comparing different AGB nucleosynthetic models and Ba star abundances based on high-resolution spectra, we are able to constrain, for example, the effect of the initial rotation velocity and the nature of the neutron source. When comparing AGB models to the extended list of heavy element abundances available for a large homogeneous observational sample of 169 Ba stars, we could confirm that the polluting AGBs are of low mass ($<4 M_{\odot}$). To identify the best fitting AGB models we used machine learning techniques and we showed that some of the stars have anomalous abundance patterns, mainly at the first s-process peak (with higher Nb, Mo and/or Ru than the models), along with high W. Additional measurements could reveal the cause for these overabundances and can help to identify the underlying processes (e.g. the i process).

Speaker: Borbála Cseh (Konkoly Observatory, HUN-REN CSFK)

109 Exploring Supernova signatures in time-resolved records from the Atacama Desert, Chile

The detection of cosmic signatures in deep-sea, ice, and lunar samples has made an important contribution to nuclear astrophysics in recent years. In particular, ${}^{60}$Fe from near-Earth supernovae has been imprinted during the time periods $2-3$ and $7-8\,\mathrm{Myr}$ ago.

This data corroborates theoretical studies that suggest that more than $10$ SNe exploded at a distance of $50-150\,\mathrm{pc}$ over the last $10-15\,\mathrm{Myr}$. Their overriding shock fronts created a volume of hot gas that is seen in observational data and referred to as the 'Local Bubble', which currently engulfs our Solar System.

We here explore for the first time sedimentary records on land, in particular from the oldest and driest desert on Earth; the Atacama Desert, Chile. In contrast to previous archives, Atacama Desert deposits are easily accessible, reach more than $10\,\mathrm{Myr}$ into the past and are not affected by continuous aqueous diffusion.

The low sedimentation rates in the Atacama Desert that are similar to deep-sea sediments, as well as the hyper-arid conditions facilitate the preservation of cosmic traces over millions of years, bearing the potential for the detection of individual supernovae within each of the broad signals.

Speaker: Jenny Feige (Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung)

110 Fast neutron induced transmission to study resonances in (α,n) reactions

Alpha-induced reactions at thermonuclear energies are difficult to measure directly, if the cross section is too low, or highly enriched isotopic material is required as target material. Transmission of fast neutrons in the MeV range can be used to find resonances that would be difficult to study in the direct reaction. In this way, the reaction ${}^{17}\mathrm{O}(\alpha,n){}^{20}\mathrm{Ne}$ which can be relevant for the neutron flux in the weak s-process can be investigated as well as ${}^{11}\mathrm{B}(\alpha,n){}^{14}\mathrm{N}$ reaction, which can act as a neutron source in first generation stars.
The fast neutron time-of-flight facility nELBE has been used to measure the total cross section of natNe and of natN in the energy range from $100\,\mathrm{keV}$ to $10\,\mathrm{MeV}$. High pressure cylindrical gas cells were used as target samples with an areal density of $0.1624$ and $0.1974\,\mathrm{atoms}/\mathrm{barn}$ respectively. The transmitted neutrons were detected using a fast $5\,\mathrm{mm}$ thick plastic scintillator with coincident read out on both ends resulting in a low detection threshold of approximately $10\,\mathrm{keV}$. In neon several previously unknown resonances were found, while in nitrogen the shape of the first resonance at $433\,\mathrm{keV}$ implies a different spin than evaluated before.

Speaker: Arnd Junghans (HZDR)

111 First evaluation of the $^{17}$O(p,$\gamma$)$^{18}$F 65 keV resonance strength by direct measurement at LUNA

The $^{17}$O(p,$\gamma$)$^{18}$F reaction plays a key role in the hydrogen burning in CNO cycle. At temperatures of interest for the H-shell burning in AGB stars, the reaction rate is dominated by the $E_\mathrm{c.m.}=65\,\mathrm{keV}$ resonance.

The strength of this resonance is presently determined only through indirect techniques, with a literature value $\omega\gamma = (16 \pm 3)\,\mathrm{neV}$, leading to an expected counting rate of $0.3\,\mathrm{reactions}/\mathrm{C}$ for typical experimental quantities.

The LUNA collaboration has recently performed a new direct measurement of the $^{17}\mathrm{O}(p,\gamma){}^{18}\mathrm{F}$ cross section focused on the $65\,\mathrm{keV}$ resonance taking advantage of the ultra-low background of the deep underground Laboratori Nazionali del Gran Sasso (LNGS, Italy) and of a high stable intense proton beam ($ \left< I \right> = 200\,\mu\mathrm{A}$) provided by the LUNA400 accelerator. For this purpose, a high sensitivity and high efficiency setup based on a segmented $4\pi$ BGO detector was developed. All these experimental efforts allowed, for the first time ever, the evaluation of the $65\,\mathrm{keV}$ resonance strength by a direct technique. Moreover, also the $\Gamma_p$ width was calculated, confirming the results of the ${}^{17}\mathrm{O}(p,\alpha){}^{14}\mathrm{N}$ $65\,\mathrm{keV}$ resonance measured in a previous LUNA experiment.

In the talk, the results of the new LUNA measurement will be presented.

Speaker: Riccardo Maria Gesue' (Gran Sasso Science Institute, INFN LNGS)

27_Poster_Gesue.pdf

112 Fully calibrated lanthanide atomic data for 3D kilonova modeling

With the detection of multiple neutron-star merger events in the last few years, the need for a more comprehensive understanding of nuclear and atomic properties has become increasingly important. Despite our current understanding, there are still large discrepancies in the opacities obtained from different codes and methods. These discrepancies lead to variations in the location and strength or absorption and emission features in radiative transfer models and prevent a firm identification of r-process products. To address this issue, we developed an optimisation technique for energy levels and oscillator strengths consistent with available experimental data. With this novel method, we can increase the accuracy of calculations while reducing the computational cost, finally making it possible to apply the method to all lanthanides instead of focusing on single ions.

We will report on converged large-scale atomic structure calculations of all singly and doubly ionised lanthanides with greatly improved transition wavelength accuracy compared to previous works. The impact of our new atomic data set on realistic 3D radiative transfer calculations and prospects of r-process signature identification will be investigated.

This work is supported by the European Research Council (ERC) under
the European Union’s Horizon2020 research and innovation programme
(ERC Advanced Grant KILONOVA No.885281)

Speaker: Andreas Floers (GSI Helmholtzzentrum für Schwerionenforschung)

Posters_NPIA_Dresden_Floers.pdf

113 Half-life and β-delayed neutron measurements of neutron-rich nuclei near N=126 at RIBF

The neutron-rich $N\sim126$ region is important to r-process calculations and has been less explored by experiments. This region is unique for its strong competition between allowed and first-forbidden transitions [1], which complicates half-life predictions. Besides, the position of the third r-process abundance peak and production of actinides are sensitive to half-lives of $N=126$ isotones [2,3]. Measurements of more exotic nuclei are essential to verify theoretical models commonly used in r-process calculations.

We will present results from the BRIKEN experiment [4] at RIBF. Particle identification was confirmed by the BigRIPS separator and a silicon energy-loss telescope. On the first attempt by RIBF, half-lives and beta-delayed neutron-emission probabilities ($P_n$) of $N\sim126$ exotic isotopes—some never been measured before—were determined by the WAS3ABi beta-counting system [5] and the BRIKEN neutron counter [6]. Preliminary results of $Z\leq79$ isotopes will be discussed.

References
[1] Zs. Podolyák, EPJ Web of Conf. 260, 03005 (2022).
[2] T. Suzuki et al., Astrophys. J. 859(2), 133 (2018).
[3] E. Holmbeck et al., Astrophys. J. 870(1), 23 (2018).
[4] T. T. Yeung et al., arXiv:2401.06428 (2024). https://arxiv.org/abs/2401.06428
[5] S. Nishimura, Prog. Theor. Exp. Phys. 2012(1), 03C006 (2012).
[6] A. Tolosa-Delgado et al., Nucl. Instrum. Methods. Phys. Res. A 925-133 (2019).

Speaker: Tik Tsun Yeung (The University of Tokyo)

114 Incorporating thermal effects into alpha decay half-life calculations for nucleosynthesis investigations

Theoretical models aiming to accurately reproduce observed nuclear abundances require complex calculations utilizing nuclear reaction networks. These networks encompass the nature of nuclear reactions and decays, accounting for both the production and destruction of nuclei. The explosive conditions in r-process sites, where temperatures rise to the order of Giga Kelvin, may lead to nuclei existing in excited states. While the effects of nuclear thermal excitations are typically considered in processes like neutron capture and photon disintegration, a similar treatment is often overlooked in the case of alpha decay. Instead, information regarding decay modes is typically derived from measurements conducted on Earth, where nuclei predominantly reside in their ground state. However, it is crucial to account for the temperature dependence of nuclear decay rates of alpha emitters. The standard formulation is achieved by summing over the half-lives of excited states of a nucleus for a specific type of decay. To facilitate a comprehensive investigation into the role of alpha decay half-lives of thermally excited nuclei in nucleosynthesis calculations, we propose an empirical formula. This formula, derived from a model for the alpha decay half-lives of excited nuclei via fitting available data, will serve to incorporate temperature-dependent half-life calculations into nucleosynthesis models.

Speaker: Diego Ferney Rojas Gamboa (Universidad de los Andes)

115 Investigating the Effects of Convective Boundary Mixing on Massive Stars at Low Z

Massive stars are not well enough understood given the important role their evolution and fates play in Galactic Chemical Evolution (GCE). One key uncertainty is convective boundary mixing (CBM), which encompasses the processes by which materials mix across the edge of convective turbulent regions inside stars. As a result of its effects on stellar structure during evolution, CBM also affects nucleosynthesis and consequently stellar yields. To investigate the importance of CBM we have computed two grids of stellar models at $Z=10^{-3}$ and two different strengths of CBM using the MESA code. The first being the typical CBM value used in literature and the second is based on the results of 3D convection simulations. In this talk, we will present a comparison of the structure of massive stars both during their evolution and at the end of their lives for these two different strengths of CBM to assess the impact of CBM on stellar evolution, SN progenitors and nucleosynthesis with a particular emphasis on the mergers of different burning shells.

Speaker: Emily Whitehead (Keele University)

114_Poster_Whitehead.pdf

116 Investigation of excited states in $^{15}$O at AGATA and Felsenkeller

The CNO cycle plays a key role in the nucleosynthesis of massive stars and their energy production. The $^{14}\mathrm{N}(\mathrm{p},\gamma){}^{15}\mathrm{O}$ reaction is the slowest in this cycle and, therefore, controls the speed of the entire cycle, influencing the synthesis of carbon, nitrogen, oxygen and fluorine. However, investigating the reaction at astrophysically relevant energies is challenging. The total reaction rate is dominated by two resonances: at $E_\mathrm{r}=259\,\mathrm{keV}$ and at $E_\mathrm{r} =-504\,\mathrm{keV}$.

While the first resonance is well understood, the impact of the subtreshold state on the $^{14}\mathrm{N}(\mathrm{p},\gamma){}^{15}\mathrm{O}$ reaction remains unclear and difficult to measure experimentally. In this work, we focus on investigating the lifetime, sub-fs range, of the $E_x = 6.793\,\mathrm{MeV}$ state in $^{15}\mathrm{O}$ to constrain the response width and therefore, its impact on the $^{14}\mathrm{N}(\mathrm{p},\gamma){}^{15}\mathrm{O}$ reaction. The experimental study was conducted in two separate campaigns at the Legnaro National Institute for Nuclear Physics in Italy (INFN), using the AGATA+SAURON array, and at the shallow-underground Felsenkeller laboratory in Germany. The Felsenkeller measurements were performed using $14.5\,\mathrm{MeV}$ and $16.9\,\mathrm{MeV}$ oxygen beams provided by the external source, which impinged on $^3$He targets. A description of the setup, target stability tests, and preliminary analysis of both campaigns will be presented.

Speaker: Max Osswald (Helmholtz Zentrum Dresden Rossendorf)

117 Late time behaviour of the kilonova light curves

Among the different signals in multimessenger astrophysics, the kilonovae are of particular interest to nuclear physicists. These electromagnetic signals can emerge from the ejecta of neutron star (NS) - NS mergers [1]. They are expected to be powered by nuclear decays since such mergers are considered dominant sites for r-process nucleosynthesis of heavy (unstable) nuclei. Even though there exist several works based on r-process network calculations, there remain loopholes in our understanding of the energy production in kilonovae. It is not easy to pin down the interplay between nuclear physics and astrophysics and new findings still emerge [2].

In this talk, we shall revisit one of the earliest kilonova models by Li and Paczynski [3] with some improvements and present a detailed analysis using all available data on the different nuclear decay modes. We shall point out some interesting features of the competition between the different decay modes at different time scales and present some hitherto unnoticed features of their role in the luminosity curves at late times.

[1] M. R. Drout et al. Science 358, 1570 (2017).
[2] Yu-Han Yang et al., Nature 626, 742 (2024).
[3] Li-Xin Li and B. Paczynski, The Astrophys. J. 507, L59 (1998).

Speaker: Dr Diego Ferney Rojas-Gamboa (Universidad de los Andes, Bogota, Colombia)

118 Low energy measurement of the ${}^{96}$Zr($\alpha$,n)${}^{99}$Mo, ${}^{100}$Mo($\alpha$,n)${}^{103}$Ru and ${}^{86}$Kr($\alpha$,n)${}^{89}$Sr reactions for studying the weak r-process nucleosynthesis

The light ($30 < Z < 45$) neutron-rich isotopes are thought to be synthesized in the neutrino-driven ejecta of core-collapse supernova via the weak r-process [1]. Recent nucleosynthesis studies have shown that $(\alpha,n)$ reactions play an important role in their production. The rates of these reactions have been calculated using statistical models, and their main uncertainty at the energies relevant to the weak r-process comes from the $\alpha+\mathrm{nucleus}$ optical potential. Several sets of parameters are available for the calculation of the $\alpha+\mathrm{nucleus}$ optical potential, leading to large deviations of reaction rates, exceeding even one order of magnitude.

To constrain the parameters of the $\alpha+\mathrm{nucleus}$ optical potential and to provide high precision reaction rates for astrophysical simulations, recently the cross sections of the $^{96}\mathrm{Zr}(\alpha,\mathrm{n}){}^{99}\mathrm{Mo}$, ${}^{100}\mathrm{Mo}(\alpha,\mathrm{n}){}^{103}\mathrm{Ru}$ and ${}^{86}\mathrm{Kr}(\alpha,\mathrm{n}){}^{89}\mathrm{Sr}$ reactions were measured at the Gamow-window for the first time [2,3]. Details on the experimental approach, on the new ATOMKI-V2 potential [4] will be presented and an outlook into the astrophysical application of the data will be provided.

[1] A. Arcones and F. Montes, Astrophys. J. 731 5 (2011).
[2] G.G. Kiss et al., Astrophys. J. 908 202 (2021).
[3] T.N. Szegedi et al., PRC 104 035804 (2021).
[4] P. Mohr et al., PRL 124 252701 (2020).

Speaker: Sándor Kovács (HUN-REN Institute for Nuclear Research)

KS_NPA_poster_id46.pdf

119 Mass measurements of neutron-rich nuclides at the N=126 shell with the FRS Ion Catcher

Direct evidence of the r-process has recently been observed in neutron star mergers, but the debate on the Nucleosynthesis environment is still far from over. Due to the scarcity of experimental information, modern r-process network calculations rely on theoretical models that give divergent predictions as one moves away from the valley of stability. Nuclear masses help to determine the r-process path and shed light on the Nucleosynthesis environment. Thus, high-precision mass measurements are performed to provide key input parameters to r-process calculations.

At GSI Darmstadt, experiments with exotic nuclides are performed, enabling the study of nuclei far from stability. These nuclei are produced at relativistic energies by projectile fragmentation or fission, separated in the fragment separator FRS and sent to the FRS Ion catcher (FRS-IC) for mass measurements utilizing its multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). An experiment was performed at the FRS-IC within FAIR Phase-0 close to the N=126 line, which is significant for nuclear structure and astrophysics studies and can help us better understand the r-process. Preliminary results from this experiment will be presented, including the first mass measurements of $^{204}Au$ and $^{205}Au$, where significant deviations from AME20 extrapolations indicate a change in the nuclear structure.

Speaker: Ms Kriti Mahajan (Justus-Liebig University, Giessen and HFHF Campus, Giessen)

120 Measurement of ${}^{26}\mathrm{Al}(n,p)$ and ${}^{26}\mathrm{Al}(n,\alpha)$ Cross Sections in Supernova Temperatures

The radioisotope ${}^{26}\mathrm{Al}$ plays a crucial role in understanding the origins of cosmic elements, particularly at active nucleosynthesis sites such as supernovae and massive star-forming regions. Its characteristic $1809\,\mathrm{keV}$ $\gamma$-ray emission, observed by gamma telescopes, serves as direct evidence of ongoing nucleosynthesis processes. Neutron-induced reactions, specifically the ${}^{26}\mathrm{Al}(n,p)$ and ${}^{26}\mathrm{Al}(n,\alpha)$ reactions, have been identified as key contributors to the ${}^{26}\mathrm{Al}$ abundance in core-collapse supernova ejecta.

Despite recent progress in measuring these reaction rates up to temperatures of $\sim 1\,\mathrm{GK}$, which are relevant to some ${}^{26}\mathrm{Al}$ creation sites, it remains insufficient for explosive scenarios occurring at temperatures between 1.5 and $3.5\,\mathrm{GK}$. Experimental data for these temperatures are currently lacking due to several challenges. These include the necessity for a powerful neutron source at the relevant energies, constraints on radioactive sample size, and difficulty measuring outgoing charged particles in high radiation environments.

In this study, we propose a novel experimental approach using the ${}^{7}\mathrm{Li}(p,n)$ reaction to generate broad-energy neutron beams. Coupled with a gaseous Micromegas detector, this setup will enable comprehensive measurement of ${}^{26}\mathrm{Al}(n,p)$ and ${}^{26}\mathrm{Al}(n,\alpha)$ reaction rates across the relevant energy range. Our study aims to advance cosmic nucleosynthesis understanding and enhance astrophysical modeling by bridging this knowledge gap.

Speaker: Mr Akiva Green (Hebrew University of Jerusalem)

NPA-XI Poster - Abstract id #150.pdf

poster pitch slide - Abstract id #150.pdf

121 Measurement of neutron capture cross section of $^{30}$Si at n_TOF

Neutron capture cross sections of $^{30}$Si are an important parameter to study the origin of silicon in our Solar System and understand isotopic abundances in SiC presolar grains. The bulk of $^{30}$Si present in our Galaxy is produced in massive stars during carbon shell burning phases and its neutron capture cross sections strongly impact on its abundance. An accurate value of the neutron capture cross section of $^{30}$Si is also needed to disentangle the contributions of the s-process nucleosynthesis to the silicon abundances measured in mainstream SiC grains in order to test stellar evolution models. Since available experimental data are scarce and discrepant (the two most recent measurements show a discrepancy in the stellar cross section of approximately a factor 2), a new accurate time-of-flight measurement was carried out during summer 2023 at the n_TOF facility at CERN. The preliminary results show important discrepancies with respect to cross sections recommended in nuclear data libraries: only one resonance at 4.98 keV is observed compared to the two resonances expected below 100 keV and an additional resonance at approximately 15.14 keV is observed. In this contribution, the motivation, the measurement and these preliminary results will be presented.

Speaker: Michele Spelta (University of Trieste & INFN - Sez. di Trieste)

Poster_NPAXI_Si30_id86.pdf

122 Measurement of neutron capture cross section of $^{64}$Ni at n_TOF

Neutron capture cross sections of $^{64}$Ni is an important parameter to accurately simulate the s-process and validate stellar models. As $^{64}$Ni is among the seeds of the s-process, the uncertainty on its capture cross section has been shown to significantly affect the predicted abundances of many isotopes produced by the s-process both in massive and AGB stars. Moreover, the uncertain value of this cross section may be the cause of the discrepancy observed between predicted and measured $^{64}$Ni isotopic ratios in SiC presolar grains. Indeed, the MACS reported by different releases of data libraries show discrepancies higher than a factor 2 at 5 keV. For these reasons, a new accurate time-of-flight measurement was carried out during summer 2023 at the n_TOF facility at CERN. The preliminary results confirm most of the resonances up to 100 keV, except for a huge resonance at 9.52 keV, reported in many of the most recent data library releases. As this resonance was expected to contribute more than 60% to the MACS at 5 keV, a significant reduction of the value reported in the most recent library releases is expected. Motivation, measurement and these preliminary results will be presented.

Speaker: Michele Spelta (University of Trieste & INFN - Sez. di Trieste)

NPAXI_Poster_Ni64_id87.pdf

123 Microscopic fission collective inertias for astrophysical applications

Nuclear fission is one of the most important nuclear phenomena and arguably its most interesting astrophysical application is in the study of r-process nucleosynthesis. The theoretical description of fission is a challenging quantum many body problem and one such key challenge is the description of collective inertias along the fission path. In most of the fission calculations, the collective inertia is evaluated using cranking approximation which neglects the dynamical residual effects. Recently, a new method for the calculation of collective inertias using finite amplitude method - quasiparticle random phase approximation (FAM-QRPA) method was devoloped which also takes into account the consistent treatment of dynamical effects neglected in cranking approximation [1]. Work is in progress in developing FAM-QRPA approach using the finite range Gogny energy density functionals and axial symmetry preserving Hartree-Fock-Bogoliubov framework to compute collective inertias needed for fission calculations. The obtained results will be then used to compute new fission reaction rates relevant for r-process calculations. This work is supported by International Graduate School (IRTG 2891) Nuclear Photonics.

1. K. Washiyama, N. Hinohara, and T. Nakatsukasa, Phys. Rev. C 103, 014306 (2021)

Speaker: Mr Nithish Kumar Covalam Vijayakumar (Technische Universität Darmstadt)

Poster_Flash#104.pdf

124 Multimessenger emission of Accretion-Induced Collapse events

An white dwarf (WD) which accreates enough mass to surpass the Chandrasekhar limit will became unstable and will initiate a collapse stage due to its own gravity. Depending on their composition and their accretion history, the collapsing WD may trigger a thermonuclear explosion (and lead to a Supernova Ia) or not. In the latter case, the collapse, completely driven by the electron capture process, will proceed until the central density reaches nuclear saturation density when the core of the collapsing star will expand abruptly and push its outer layers in an outwards motion. To the second scenario, where a proton-neutron star is left as an remnant, it is given the name of accretion-induced collapse (AIC). Due to the accretion history of AICs and their highly spinning and (probably) magnetized remnant, these events have historically been proposed as the engines of short gamma-ray bursts and millisecond pulsars. AIC are also related to the nucleosynthesis of rare neutron-rich isotope, due to the (initially) low electron-fraction content of their ejecta. In this talk, we will explore different aspects of AICs, exploring for example the imprint of the progenitor angular momentum on their multimessenger emission.

Speaker: Luis Felipe Longo Micchi (Friedrich-Schiller Universitat)

125 Neutron-capture in the wild: finding r-process enhanced metal-poor stars in the Milky Way and beyond

The lowest metallicity stars in the Milky Way Halo are the fossil records of the earliest star-forming environments in the universe. Their chemical abundance patterns help us understand primordial nucleosynthesis, the mass function of the first stars, and the pathways that led to the chemical complexity we observe today. However, there is still debate about when (and for how long) the universe transitioned from metal-free to the first chemical enrichment episodes that triggered low-mass star formation. In that context, metal-poor stars with enhancements in elements formed by the r-process can hold valuable clues to this intricate cosmic puzzle. Such stars are rare and difficult to find. In this presentation, I will talk about the serendipitous discovery and chemo-dynamical analysis of SPLUSJ1424, an old, low-mass, extremely metal-poor halo star enhanced in elements formed by the r-process. At [Fe/H]=-3.39, this is one of the lowest metallicity stars with measured Th and has the highest Th/Eu ratio observed to date, making it part of the "actinide-boost" category. Analysis suggests that the gas cloud from which SPLUSJ1424-2542 was formed must have been enriched by at least two progenitor populations, including a supernova explosion of metal-free stars and a neutron star merger event.

Speaker: Vinicius Placco (NSF NOIRlab)

poster_placco.pdf

slide_placco.pdf

126 New half-lives and $\beta$-delayed neutron branchings for Ba to Nd nuclei (A$\sim$160) for r-process rare-earth nucleosynthesis

The rapid neutron capture process (r-process) is a key mechanism responsible for producing nearly half of the nuclei heavier than iron in explosive scenarios. In the solar-system abundance pattern, the Rare-Earth Peak (REP) around mass number $A = 160$ represents a significant feature resulting from freeze-out during the final stages of neutron exposure. The BRIKEN collaboration [1] conducted extensive measurements of $\beta$-decay properties of nuclei of interest to better understand the r-process at the Radioactive Isotope Beam Factory (RIBF), RIKEN Nishina Center, Japan. Our study focuses on the Barium to Neodymium region crucial for REP r-process nucleosynthesis [2,3]. In this contribution, we present the final experimental results from the BRIKEN-REP experiment, which yielded new $T_{1/2}$ and $P_{1n}$ branching ratios. Furthermore, we discuss the implications of these findings for global models of nuclear structure, aiming to refine theoretical predictions and enhance our understanding of REP r-process nucleosynthesis.

[1] J.L. Tain et. al , Acta Physica Polonica B {49(03), 417 $-$ 428 (2018).
[2] M. R. Mumpower et al , Phys. Rev. C 85, 045801 (2012).
[3] A. Arcones and G. Martinez Pinedo , Phys. Rev. C 83, 045809 (2011).

Speaker: Max Pallas I Solis (Universitat Politècnica de Catalunya (UPC))

127 NG-Trap: System for Measuring Neutron Capture Cross-sections of Short-lived Fission Fragments

Almost all nuclei heavier than iron are produced through neutron capture nucleosynthesis, about half of them by the rapid (r) process. One of the limiting factors in understanding the r-process is the need for neutron capture cross-section measurements on unstable nuclei. As shown with the recent measurement of $^{88}$Zr (Shusterman et al., Nature 2019), neutron capture cross-sections can exhibit unpredictable behaviour.

We propose a novel method of measuring neutron capture cross-sections of short-lived nuclei. Neutron-rich nuclei produced via neutron-induced fission inside of a gas-filled stopping cell will form a mass-selected cooled low-energy beam, which will be transported into a linear Paul trap (coined ‘NG-Trap’), forming a target. This ‘cloud target’ of up to $10^{10}$ ions will then be irradiated with neutrons. The reaction products will then be identified and counted using a multiple-reflection time-of-flight mass-spectrometer (MR-TOF-MS), thus extracting the capture cross-sections.

This poster will present a breakthrough achievement towards the goal of generating the required ‘cloud target’. A demonstrator system with an ion capacity of more than $10^{10}$ ions will be presented. This system is a major milestone of the plan to install a high-capacity trap at the Soreq Applied Research Accelerator Facility (SARAF), currently under construction in Yavne, Israel.

Speaker: Heinrich Wilsenach (Justus-Liebig-Universität/Tel Aviv University)

128 Nuclear pasta in neutron stars

Theory has long predicted that a dense mantle consisting of exotic nuclear structures known as “nuclear pasta” exists between the crust and the core of a neutron star. Studying this possible phase of dense matter is important since its transport and mechanical properties differ markedly from those of the crust. Different types of pasta would thus leave an imprint on many observable aspects of neutron stars, from their magnetothermal evolution to the gravitational waves they emit. In this contribution, I study the emergence of pasta phases with parameterizations of a nuclear energy density functional that were accurately calibrated to both (I) thousands of experimental data points on nuclear structure and (ii) state-of-the-art ab initio predictions for dense matter. I will compare different levels of approximations: starting from a semi-classical approach in one dimension up to fully quantum-mechanical simulations in three dimensions. In particular, I will show how the inclusion of quantum effects in the modeling impacts the formation of nuclear pasta.

[1] N. N. Shchechilin, N. Chamel, J. M. Pearson, Physical Review C, 108, 025805 (2023)

Speaker: Nikolai Shchechilin (Universite Libre de Bruxelles)

EPJA2_NikolaiShchechilinIMG_3446.JPG

IMG_3561.JPG

poster_Dresden.pdf

129 Nuclear Physics Experiments at the Bremsstrahlung Facility $\gamma$ELBE

Photon-induced reactions are interesting tools for nuclear-structure and nuclear-astrophysics experiments. In particular, the photon-scattering or nuclear-resonance-fluorescence method can gain unique information about nuclear excitations with low spin. Excitations close to the neutron-separation energy attract growing interest because they may reveal information about new excitation modes and because they are of relevance for the astrophysically important photodissociation. In order to study such excitations, photon-scattering experiments with beams of high intensity at electron energies greater than 10MeV are necessary. Such beams are available at the $\gamma$ELBE facility at Helmholtz-Zentrum Dresden-Rossendorf. The superconducting electron accelerator ELBE delivers an electron beam of tunable energy between 7 and 18 MeV with a continuous-wave repetition rate of 13 MHz and a mean current of up to 1 mA which is used to produce high intensity bremsstrahlung of variable endpoint energy. The $\gamma$ELBE beam line and the experimental area were designed such that the production of neutrons and the scattering of photons from surrounding materials are minimized. A dedicated experimental setup of large volume HPGe detector has been build to enable high resolution $\gamma$-ray detection.
Therefore, $\gamma$ELBE offers outstanding possibilities for nuclear-structure studies up to and beyond the particle-separation energies and for the investigation of astrophysical problems.

Speaker: Ronald Schwengner (HZDR)

130 Nucleosynthesis and Kilonova in Neutron Star Mergers: Impact of Nuclear Matter Properties

Matter expelled from binary neutron star (BNS) mergers can harbor r-process nucleosynthesis and power a Kilonova (KN). Both the elemental yields and the KN transient are intimately related to the astrophysical conditions of the merger ejecta, which in turn indirectly depend on the equation of state (EOS) describing the nuclear matter inside the NS. In particular, the merger evolution is influenced by the nuclear matter properties that characterize the EOS around and above nuclear saturation density.

We consider the outcome of a set of BNS merger simulations employing different finite-temperature nuclear EOSs, obtained from Skyrme-type interaction models. We study the ejecta using a nuclear reaction network coupled with a semi-analytic KN model.

The final elemental abundances and the associated KN light curves are found to be non-trivially influenced by the nuclear matter properties used to parametrize the EOS, specifically the incompressibility and the nucleon effective mass at saturation density. A major role is played by the overall amount of each ejecta component, highlighting the strong degeneracy that intervenes between the merger outcome and the behaviour of the intrinsic nuclear matter.

Speaker: Giacomo Ricigliano (Technical University of Darmstadt)

Poster_NPAXI.pdf

131 Probing the deconfinement phase transition in hybrid stars with the fastest-spinning millisecond pulsars

We study the properties of hybrid stars containing a color superconducting quark matter phase in their cores, described by the chirally symmetric formulation of the confining relativistic density functional approach. It is shown that depending on the dimensionless vector and diquark couplings of quark matter, the characteristics of the deconfinement phase transition are varied, allowing us to study the relation between those characteristics and mass-radius relations. Moreover, we show that the quark matter equation of state (EoS) can be nicely fitted by the Alford-Braby-Paris-Reddy model that gives a simple functional dependence between the most important parameters of the EoS and microscopic parameters of the initial Lagrangian. The developed approach is utilized for analyzing spinodal instability of quark matter and constructing hybrid quark-hadron EoS. Based on it, we analyze the special points of the mass-radius diagram in which several mass-radius curves intersect. Using the found empirical relation between the mass of the special point, the maximum mass of the mass-radius curve, and the onset mass of quark deconfinement, we constrain the range of vector and diquark couplings of the quark matter model. In addition, we construct a family of curves, which allow us to describe the black widow pulsar PSR J0952-0607.

Speaker: Christoph Gartlein (University of Lisbon)

Flash talk_new.pdf

132 Re-visiting the role of short-range correlations on neutron star properties

Role of short-range correlations (SRCs) on properties of the neutron stars is re-examined by considering the behaviour of low density part of the equation of state, such that bulk properties of finite nuclei such that binding energy, charge radius, iso-scalar giant monopole resonance etc. remains unaffected with the addition of SRCs, within the framework of relativistic mean-field (RMF) models. Parameters of RMF models are re-calibrated by matching the behaviour of equation of state at sub-saturation densities rather than at single saturation density point, when SRCs are incorporated in such models. Relative response of energy of symmetric nuclear matter and density dependence of the nuclear symmetry energy towards SRCs governs the overall behaviour of equation of state of neutron star and may become softer or stiffer with the inclusion of SRCs for different types of interactions in the RMF model. The inclusion of short-range correlations in a few recently advocated equations of state brings the values of dimensionless tidal deformability closer to constrained limits from the GW170817 event.

Speaker: Mr Anagh Venneti (Department of Physics, BITS Hyderabad, India)

133 Repairing $^{205}$Pb as an early Solar System chronometer by measuring the bound-state beta decay of $^{205}$Tl

Lead-205 looks like a promising cosmochronometer for the early Solar System due to its unique position among astrophysically short-lived radionuclides as an s-only isotope probing the termination of the s process [1]. Unfortunately, the 2.3 keV first excited state in $^{205}$Pb reduces the half-life in stellar environments by around 6 orders of magnitude, which could severely inhibit $^{205}$Pb production. However, Yokoi et. al. [2] pointed out that the bound-state $\beta$ decay of $^{205}$Tl could counter-balance this decay by producing $^{205}$Pb. To clarify the complex production of $^{205}$Pb, we measured the bound-state $\beta$ decay of $^{205}$Tl$^{81+}$ at the Experimental Storage Ring in GSI, Darmstadt. From the measured half-life, we calculated new weak decay rates for a wide range of astrophysical conditions. AGB stellar nucleosynthesis models based on these new rates saw approximately a factor 2 increase in $^{205}$Pb production (when legacy rates were controlled). With new production ratios, we predicted an updated steady-state interstellar medium (ISM) $^{205}$Pb/$^{204}$Pb ratio. By comparing the ISM ratio to the ratio measured in the earliest meteorites, we derived, for the first time, a positive time interval for the isolation period of the solar material from enrichment.
[1] Lugaro (2018) PPNP 102:1–47.
[2] Yokoi (1985) A&A 145:339–346.

Speaker: Dr Iris Dillmann (TRIUMF)

134 Resolving the discrepancies in the spectroscopy of ${}^{39}$Ca for the $^{38}$K($p$,$\gamma$)$^{39}$Ca reaction

Elemental abundances are excellent probes of classical novae (CN). Sensitivity studies show that $^{38}$K($p$,$\gamma$)$^{39}$Ca reaction-rate uncertainties modify the abundance of calcium by a factor of 60 in CN ejecta. Existing direct and indirect measurements are in contradiction concerning the energies and strengths of important resonances in the $^{38}$K($p$,$\gamma$)$^{39}$Ca reaction. Direct measurements of the lowest three known $\ell = 0$ resonances at $E_\mathrm{r} = 386, 515, \text{ and } 679\,\mathrm{keV}$ have greatly reduced the uncertainties on the reaction rate for this reaction. A subsequent $^{40}$Ca($^{3}$He,$^4$He)$^{39}$Ca experiment using the SplitPole at TUNL concluded that one of the resonances ($E_\mathrm{r}$ = 701.3 or $E_\mathrm{r}$ = 679 keV depending on the source of the nuclear data) may have been misplaced in the DRAGON target during the direct measurement and that tentative new states at $E_\mathrm{x} = 5908, 6001, \text{ and } 6083\,\mathrm{keV}$ ($E_\mathrm{r} = 137, 230, \text{ and } 312\,\mathrm{keV}$) could correspond to important resonances in $^{38}$K($p$,$\gamma$)$^{39}$Ca. To resolve these, $^{39}$Ca was studied using the $^{40}$Ca($p,d$)$^{39}$Ca reaction at forward angles with a proton beam energy of $66\,\mathrm{MeV}$ using the K600 magnetic spectrometer. These measurements are aimed at verifying the properties of levels in the region where discrepancies between various experiments persist. Preliminary results will be presented.

Speaker: Sifundo Binda (University of the Witwatersrand and iThemba LABS)

135 Results of cross-section measurements of proton-capture reactions on stable Rubidium isotopes

The existence of some stable neutron deficient nuclei - the p nuclei - can not be explained by neutron-capture processes [1]. Therefore, other types of reactions - dominantly photodisintegration reactions - come into play. This is called the $\gamma$ process. Statistical model calculations play a crucial role in modelling this process as cross sections for many of these photodisintegration reactions are not known trough experiments.

Two in-beam experiments were performed at the University of Cologne's high-efficiency HPGe $\gamma$-ray spectrometer HORUS to study the $^{85,87}$Rb$(p, \gamma)^{86,88}$Sr reactions. A 10 MV FN Tandem accelerator provided proton beams between $E_p = 2$ and $5$ MeV. Total cross-section values were determined for six different proton-beam energies for the $^{87}$Rb$(p, \gamma)^{88}$Sr reaction and for three different proton-beam energies for the $^{85}$Rb$(p, \gamma)^{86}$Sr reaction. These first experimental cross-section values for the $^{85,87}$Rb$(p, \gamma)^{86,88}$Sr reactions help to constrain the nuclear physics input for statistical model calculations.

Supported by the DFG (ZI 510/8-2).

[1]T. Rauscher \textit{et al}., Rep. Prog. Phys. \textbf{76} (2013) 066201.

Speaker: Ms Svenja Wilden (University of Cologne, Institute for Nuclear Physics)

130_Poster_Wilden.pdf

136 S-Process Nucleosynthesis in and from AGB Stars

The nucleosynthetic s-process occurring in AGB stars from 1-6 M is responsible for creating half of the heavy elements in the universe. The s-process can be traced directly through AGB stars, or indirectly through their binary companions (Ba, CEMP-s, CH stars), as AGBs will dredge s-process material to the surface and deposit this material onto the companion.

We present data for 30 stars including AGB, CEMP-s, Ba, and CH stars. We derive atmospheric parameters using ATHOS and compute 1D LTE abundances with MOOG, focusing on elements created by thermally pulsing AGB stars (C, Sr, Y, Zr, Mo, Ba, La, Ce, Nd, Pb), and Eu. We monitor RVs to investigate binary properties.

Comparing our abundances to FRUITY yields we estimate masses of AGB stars, and we investigate correlations in abundance space. With detailed modelling of orbits using the ELC program, we estimate dynamical masses and orbital parameters. For our systems and data from Hansen+ 2019 and Placco+ 2014, we investigate efficiencies of AGB wind mass transfer and stellar mixing processes by simulating binary accretion using the STARS code. Our results show correlations between AGB and companion masses from abundance patterns and dynamical masses. This work has implications for galactic chemical evolution.

Speaker: Alexander Jordan Dimoff (Max Planck Institute für Astronomie)

123_Poster_Dimoff.pdf

137 Search for r-process Pu-244 in the K-Pg boundary layer

The K-Pg (Cretaceous–Paleogene) boundary at 66 Ma marks one of five major mass extinctions in Earth’s fossil history. Based on strong enrichments of platinum-group elements, Alvarez et al. [1], in 1980, suggested that the impact of a large asteroid was responsible for the K/Pg event. To exclude other causes for the mass extinction, e.g., a nearby supernova(SN)-explosion, they also searched for a long-lived radionuclide, $^{244}$Pu (t$_{1/2}$=81 Myr), assuming that this is predominantly produced and ejected in SNe. No $^{244}$Pu was detected, leaving an impact as the most plausible cause. This was also confirmed by discovering the Chicxulub impact structure.
However, since 1980, strong evidence evolved that heavy r-process elements, like $^{244}$Pu, are produced in rare explosive events [2]. Furthermore, the method of Accelerator Mass Spectrometry has since emerged with superior detection efficiency for $^{244}$Pu [3]. The enormous gain in sensitivity prompted us to reinvestigate the $^{244}$Pu content in the K-Pg boundary layer, despite the overwhelming evidence for an asteroid impact. However, no enhanced $^{244}$Pu concentration was found, again ruling out the SN hypothesis.
[1] Alvarez et al., Science 208 (1980) 1095. [2] Wallner et al., Science 372 (2021) 742. [3] Fields, Wallner, Annu. Rev. Nucl. Part. Sci. 73 (2023) 365.

Speaker: Sebastian Fichter (Helmholtz-Zentrum Dresden-Rossendorf)

NPA-2024_Poster-Flash_SF.pdf

NPA-XI-ID_131_Poster_K-Pg_SF.pdf

138 Search for Supernova-produced $^{60}$Fe in Antarctica Tracing the Local Interstellar Cloud

The presence of long-lived radionuclides provides insights into the solar system's history. The radionuclide $^{60}$Fe (t$_{1/2}\,$=$\,$2.6$\,$Myr) is mainly synthesized in massive stars and subsequently ejected by supernovae. Embedded into dust grains, $^{60}$Fe can enter the solar system and be deposited into terrestrial archives, where it evidences stellar explosions even after several million years.

Expanding upon the discovery of increased levels of $^{60}$Fe in million year old deep-ocean material and a recent influx into Antarctic snow, we now aim to investigate the influx pattern in the unexplored time interval 50$\,-\,$80$\,$kyr before present. A 300$\,$kg sample of the Antarctic EPICA Dronning Maud Land (EDML) ice core was selected to probe the recent $^{60}$Fe influx and implications for the formation of the Local Interstellar Cloud. Benefiting from their remoteness, Antarctic ice cores offer a unique geological archive with minimal terrestrial contamination.

The ultra-low deposition of a few $^{60}$Fe atoms per cm$^{2}$ per year can only be investigated by accelerator mass spectrometry. The DREAMS facility (HZDR) was used to measure the cosmogenic radionuclides $^{10}$Be, $^{26}$Al and $^{41}$Ca, whereas HIAF (ANU), as the sole capable facility worldwide, is required for measurements of $^{53}$Mn and $^{60}$Fe. We report on the recent results of this project.

Speaker: Annabel Rolofs (Helmholtz-Zentrum Dresden-Rossendorf)

NPAXI_Rolofs_ID166.pdf

139 Shedding light on the brightest supernovae

Superluminous supernovae are a class of exceedingly bright transients whose luminosity cannot be comfortably explained by the standard 56Ni-decay picture. The quest for an alternative scenario has pointed at the contribution of a nascent millisecond magnetar and/or at the interaction of the supernova ejecta with a circumstellar medium surrounding the progenitor star; however, some of the observed photometric and spectroscopic features of many superluminous supernovae are seemingly reminiscent of a 56Ni-decay contribution. I present the results of the spectrophotometric observational campaigns of three superluminous supernovae and discuss the observational data in the framework of the magnetar and the circumstellar-interaction scenario, and I suggest that some superluminous supernovae might be the UV-optical-NIR counterpart of a magnetorotational instability-driven core collapse.

Speaker: Achille Fiore (Goethe Universität Frankfurt am Main)

140 Shell model description of the spectroscopic properties of the Aluminum isotopes of astrophysical interest

The Al-Mg cycle is a crucial pathway in stellar nucleosynthesis. In this cycle, various aluminum (Al) isotopes are synthesized through several nuclear reactions onto magnesium (Mg) isotopes, followed by subsequent nuclear transformations within stellar environments. One of these reactions is the rp-process, in which, spin-parity assignments play an essential role in determining the rates at which reactions occur.
In the context of calculating reaction rates for the rp-process, the spin and parity assignments derived from the shell model are crucial inputs.
We are interested in our work to the study, within the shell model framework, of the structure of the Al isotopes (with A= 24 to 27) produced through rp-process.
A complete spectrum has been calculated, using the PSDPF interaction, for each isotope and has been compared to available experimental data. Prediction of spin-parity assignments for the unknown states in all isotopes has been proposed, particularly, at excitation energies of astrophysical relevant. A detailed discussion of our study will be presented in our contribution.

Speaker: Prof. Mouna Bouhelal (LPAT, Echahid Cheikh Larbi Tebessi University)

141 Stelle Sulla Terra: The advantages of making science accessible

Nuclear astrophysics is a field of research that lends itself to an engaging dissemination thanks to its interdisciplinary nature. It is important to involve blind or deaf individuals in these moments of dissemination to an even greater extent. The project ‘Stelle sulla Terra’ at the University of Padua aims to achieve this by reproducing a scaled model of the ‘Bellotti’ IBF facility and creating other tactile materials and videos using sign language.”

Speaker: Antonio Caciolli (University and INFN of Padova)

NPAXI_2024_Caciolli_TM.pdf

142 The $^{140}$Ce(n,$\gamma$) cross section measured at n_TOF and its astrophysical implications

The slow (s) and rapid (r) neutron-capture processes are major producers of elements heavier than iron. The main component of the s-process takes place in low-mass AGB stars, through a series of neutron capture reactions and beta decays, resulting in a flow that proceeds along the beta-stability valley. In this context, the neutron-capture cross sections of closed neutron shell nuclei represent bottlenecks for the s-process. Among them, $^{140}$Ce is particularly interesting because of a discrepancy between stellar model predictions and observations of stars belonging to the Globular Cluster M22. This discrepancy triggered the n_TOF collaboration to measure the $^{140}$Ce neutron capture cross section in a wide neutron energy range at the n_TOF facility, combined with a highly enriched $^{140}$Ce sample and an experimental setup based on four low neutron sensitivity liquid scintillations detectors. The high accuracy, high-resolution data of n_TOF have led to a Maxwellian Averaged Cross Sections (MACS) with an uncertainty better than 5%. At low energy, the new value is up to 40% larger than the available library evaluations. This new value, however, did not solve the existing discrepancy, possibly indicating the presence of additional nucleosynthesis processes. I will present the n_TOF measurement and its astrophysical implications.

Speaker: Dr Rudra N. Sahoo (INFN Sezione di Bologna)

143 The 12C+12C reaction at the Bellotti Ion Beam Facility - The setup development

The 12C+12C fusion reaction plays an significant role in our understanding of heavy element nucleosynthesis, as well as supernovae of type Ia. Two of its channels, namely $^{12}$C($^{12}$C,p)$^{23}$Na and $^{12}$C($^{12}$C,$\alpha$)$^{20}$Ne are currently under study at the Bellotti Ion Beam Facility within an energy range from 2$\,$MeV to 3.5$\,$MeV. While the first phase is focussing on 2.0$\,$MeV to 2.2$\,$MeV, where there is no direct measurement as of today, future upgrades will try to cover the entire Gamow window.
The experimental approach is based on water-cooled, solid graphite targets, as well as a 150% HPGe detector and a segmented NaI detector in close geometry surrounded by a massive lead castle. This contribution will report on the development of the experimental setup, as well as on a dedicated target study, which was done at the Felsenkeller shallow-underground laboratory in Dresden.

Speaker: Dr Steffen Turkat (Università di Padova)

144 The deep underground "Bellotti Ion Beam Facility" at the Gran Sasso National Laboratories

The Bellotti Ion Beam Facility was inaugurated in 2023. It currently houses a 3.5 MV Singletron accelerator supplied by High Voltage Engineering Europe, installed inside the deep underground Laboratori Nazionali del Gran Sasso (LNGS) in Italy, where the natural cosmic ray flux is reduced by up to six orders of magnitude. The installation of the facility has been supported by the "LUNA-MV Premium Funds" provided by the Italian Ministry of Research and by INFN.

The intense proton, alpha and carbon beams available at the Bellotti Ion Beam Facility are made available to the international scientific community through annual calls for beam time published on the LNGS website.

This presentation will outline the main characteristics of the facility, its operational status and future developments.

Speaker: Matthias Bernhard Junker (Laboratori Nazionali del Gran Sasso - INFN)

2024-09-16_NPA-Xi_Dresden_Junker.pdf

Bellotti-IBF_Presentation-Slide.pdf

145 The direct determination of the cross section of the 12C + 12C reaction at astrophysical energies

Carbon burning is the third stage of stellar evolution determining the final destiny of massive stars and of low-mass stars in close binary systems. Only stars with a mass larger than a critical value $M^{*}_{up}\sim10M_\odot$, can ignite C in non-degenerate conditions and proceed to the next advanced burning stages up to the formation of a gravitationally unstable iron core. Various final destinies are possible, among which a direct collapse into a black hole or the formation of a neutron star followed by the violent ejection of the external layers (type II SN). Less massive stars $M

$^{12}C+^{12}C$ fusion reactions were investigated in a wide energy range, down to 2.1MeV, still above the astrophysical energies.
Only indirect measurement covers those energies with contradictory results. A direct measurement down to the Gamow peak is therefore crucial.

The aim of the LUNA collaboration is the direct determination of the cross section of the $^{12}C+^{12}C$ reaction at astrophysical energies through $\gamma$ spectroscopy at LNGS. Here a devoted setup is being developed to reach an extremely low background condition. The experiment will make use of the new MV accelerator available at the Bellotti Ion Beam Facility at LNGS, in the context of the LUNA MV research project. This accelerator is capable of producing a high intensity carbon beam ($150\mu A$ for a beam of $^{12}C^+$ and $50p\mu A$ for a beam of $^{12}C^{++}$) with great energy resolution and stability. The detection setup will be made of several NaI scintillators and an HpGe. NaI detectors will be placed in a compact arrangement around the HpGe, covering a $\sim3.5\pi$ solid angle: such a configuration guarantees a high detection efficiency, while preserving the excellent HpGe resolution (1.2keV at 1.33MeV).
The NaI configuration will also function as an active veto for Compton, environmental radioactivity and beam-induced background events.
The detectors array will be placed in a 2cm thick copper shielding surrounded by a 25cm lead shielding which will further reduce the
environmental background of more than 2 orders of magnitude.

With this setup, we'll also be able to measure the level density of $^{24}Mg$
through the de-excitation of $^{20}Ne$ and $^{23}Na$ nuclei.
This will allow us
to explore the possible cluster structures of the $^{24}Mg$ nucleus. In
particular, we'll be able to examine the $E_{cm}=1.5\,MeV\,-\,4\,MeV$ energy
window (15.44 MeV to 17.94 MeV considering the Q-value), where the
cluster states could be found.

With my contribution I will present an overview of the experiment setup and development, together
with details on Geant4 simulations and preliminary measurements.

Speaker: Riccardo Maria Gesue' (Gran Sasso Science Institute, INFN LNGS)

178_Poster_Gesue.pdf

146 The i-process in AGB stars with Overshoot

The production of neutron-rich elements at neutron densities intermediate to those of the s- and r-processes, the so-called i-process, has been identified as possibly being responsible for the observed abundance pattern found in CEMP-r/s stars. The production site may be low-metallicity stars on the Asymptotic Giant Branch where the physical processes during the thermal pulses are not well known. In this talk I will present models of a 1.2 M⊙ , Z=5 × 10−5 star, exploring the impact of overshoot parameters on proton ingestion events (PIEs) and the neutron densities as a necessary precondition for the i-process. In addition, light element abundances in our models can be leveraged to favor certain sets of overshoot parameters.

Speaker: Bryce Remple (Max-Planck-Institut fuer Astrophysik)

Poster174_digital.pdf

147 The New Deep-underground Direct Measurement of ${}^{22}\mathrm{Ne}(\alpha,\gamma){}^{26}\mathrm{Mg}$ with EAS$\gamma$: a feasibility study

The reaction ${}^{22}\mathrm{Ne}(\alpha,\gamma){}^{26}\mathrm{Mg}$ is associated with several questions in nuclear astrophysics, such as the Mg isotope ratio in stellar atmospheres and the nucleosynthesis of elements beyond Fe through its competition with the neutron source ${}^{22}\mathrm{Ne}(\alpha,n){}^{25}\mathrm{Mg}$.

Due to the low stellar energies and therefore very low cross section, direct experiments have been only able to provide upper limits below a strong resonance at $832\,\mathrm{keV}$.

The purpose of the EAS$\gamma$ project is to perform the first direct measurement of the ${}^{22}\mathrm{Ne}(\alpha,\gamma){}^{26}\mathrm{Mg}$ in the range of astrophysical interest below $600-800\,\mathrm{keV}$ and the remeasurement of the important $832\,\mathrm{keV}$ resonance.

The measurement will be performed at Laboratori Nazionali del Gran Sasso and will be carried out using a high $\alpha$ particle current delivered by the newly commissioned LUNA MV accelerator.

Moreover, its position underground and additional passive shielding will reduce the $\gamma$-background, drastically increasing the sensitivity over the state of the art. The $\gamma$-rays produced in the reaction will be detected by a NaI scintillator array surrounding a windowless, recirculating gas target.

I will present the current status of the project and the preliminary results of NaI detector array simulation and characterisation.

Speaker: Daniela Mercogliano (INFN-Na and Unina)

037_Poster_Mercogliano.pdf

148 The quest for detection of $^{182}$Hf in Earth’s archives - new techniques in Accelerator Mass Spectrometry for the search of live nucleosynthesis signatures

Accelerator mass spectrometry (AMS) is commonly the most sensitive technique for detection of long-lived isotopes and has allowed identification of $^{60}$Fe and $^{244}$Pu signals in terrestrial and lunar archives from recent nearby nucleosynthesis.
Belonging to the middle-mass region of r-process nuclides, $^{182}$Hf (T$_{1/2}$=8.9$\,$Ma) could potentially be produced in different scenarios to those for $^{244}$Pu. However, AMS detection of astrophysical $^{182}$Hf has failed up to now due to the strong interference from its ubiquitous stable isobar $^{182}$W. Based on various yield- and elemental-ratio-calculations for possible $^{182}$Hf production scenarios, the estimated $^{182}$Hf/Hf signal intensity is at most a few times 10$^{−13}$, about two orders of magnitude below classical AMS sensitivity limits.

The novel Ion-Laser InterAction Mass Spectrometry (ILIAMS) technique achieves near-complete suppression of isobars via selective laser photodetachment and chemical reactions of decelerated anion beams in a gas-filled radio frequency quadrupole. It enables suppression of $^{182}$WF$_5$$^−$ vs. $^{182}$HfF$_5$$^−$ by >10$^5$ resulting in a W-corrected blank value of $^{182}$Hf/$^{180}$Hf=(3.4$\pm$2.1)$\times$10$^{–14}$.

We will highlight the potential of ILIAMS for sensitive detection of previously inaccessible long-lived radioisotopes and discuss ways to proceed in order to detect $^{182}$Hf at astrophysical levels including the challenges this poses in chemical sample preparation of HfF$_4$ from 100$\,$gram-amounts of deep-sea archives.

Speaker: Martin Martschini (University of Vienna, Faculty of Physics – Isotope Physics, VERA Laboratory, Vienna, Austria)

Poster #128_Martschini_182Hf.pdf

Poster Pitch #128_Martschini_182Hf.pdf

149 The SHADES Project: Underground Measurement of the Low Energy ${}^{22}$Ne($\alpha$,n)${}^{25}$Mg Cross Section

Synthesis of neutron-rich isotopes is widely considered to occur via the slow neutron-capture processes (weak and main s-process). The reactions ${}^{13}\mathrm{C}(\alpha,\mathrm{n}){}^{16}\mathrm{O}$ and ${}^{22}\mathrm{Ne}(\alpha,\mathrm{n}){}^{25}\mathrm{Mg}$ are the main neutron sources for this process; the LUNA collaboration has measured the former reaction to high precision at energies relevant for AGB stars ($>90\,\mathrm{MK}$). However, the latter reaction remains experimentally unconstrained at the astrophysically relevant temperatures for helium shell burning, $0.2–0.3\,\mathrm{GK}$, or centre-of-mass energies $450–750\,\mathrm{keV}$. In particular, the state-of-art reaction rate is represented only by an upper limit at energies below $680\,\mathrm{keV}$. To address this knowledge gap, a recent campaign is ongoing using the LUNA-MV accelerator to directly measure the ${}^{22}\mathrm{Ne}(\alpha,\mathrm{n}){}^{25}\mathrm{Mg}$ cross section in the astrophysical energy range. This experiment will exploit the new neutron counter array SHADES installed downstream from a ${}^{22}\mathrm{Ne}$ gas target. Thanks to the very low natural neutron background at the Laboratori Nazionali del Gran Sasso and the innovative SHADES array, the rate is envisioned to have an improved sensitivity of $> 2$ orders of magnitude over previous measurements. This poster will present an overview of the SHADES array along with preliminary results collected at and above the important $704\,\mathrm{keV}$ resonance using the LUNA-MV accelerator.

Speaker: Thomas Chillery (Laboratori Nazionali del Gran Sasso)

036_Poster_Chillery.pdf

150 The SOCIAL project: measurement of the ${}^{14}\mathrm{N}(p,\gamma){}^{15}\mathrm{O}$ cross section

Solar neutrinos play a significant role in constraining physical conditions in the interior of the Sun and are a unique tool to investigate its core composition. The ${}^{14}\mathrm{N}(p,\gamma){}^{15}\mathrm{O}$ cross section is the dominant error source on neutrino flux predictions. At solar energies ($15 - 50\,\mathrm{keV}$) such a cross-section is too low to be measured directly, therefore current estimates are based on extrapolations of higher-energy data. The SOCIAL project aims at determining the ${}^{14}\mathrm{N}(p,\gamma){}^{15}\mathrm{O}$ reaction rate at astrophysical energies with $5\%$ precision, as requested by Solar models. We take advantage of the much suppressed gamma-ray background achievable in the underground Gran Sasso laboratory to measure the ${}^{14}\mathrm{N}(p,\gamma){}^{15}\mathrm{O}$ cross section in the $50-370\,\mathrm{keV}$ energy range. We deliver an intense proton beam from the LUNA accelerator to a solid nitrogen target. Gamma-rays are detected with a high-efficiency $4\pi$-BGO detector composed of 6 independent segments. The data analysis technique will lead to determine the total and the partial cross sections for individual gamma transitions. An overview of the experimental setup and the preliminary data analysis will be presented.

Speaker: Dr Giulia Gosta (Università degli Studi di Milano and INFN Milano)

IMG_3551.JPG

NPA_1slide_Giulia_Gosta.pdf

NPA-poster.pdf

NuPECC_GiuliaGosta_IMG_3460.JPG

151 Unraveling the global behavior of equation of state by explicit finite nuclei constraints

We obtain posterior distribution of equations of state (EOSs) across a broad range of density by imposing explicitly the constraints from precisely measured fundamental properties of finite nuclei, in combination with experimental data from heavy-ion collisions and astrophysical observations of radius, tidal deformability and minimum-maximum mass of neutron stars. The acquired EOSs exhibit a distinct behavior compared to those usually obtained by imposing the finite nuclei constraints implicitly through empirical values of selected key parameters describing symmetric nuclear matter and symmetry energy in the vicinity of saturation densities. The explicit treatment of finite nuclei constraints yields softer EOSs at low densities which eventually become stiffer to meet the maximum mass criteria. The radius measurements derived from NICER and HESS J1731-347 exhibit favorable agreement with the posterior distribution of radius determined through our explicitly constrained EOSs. The Kullback-Leibler divergence has been used to perform a quantitative comparison of the distributions of the EOSs resulting from implicit and explicit finite nuclei constraints.

Speaker: Anagh Venneti (Department of Physics, Birla Institute of Technology and Science Pilani, Hyderabad Campus, Hyderabad-500078,India)

152 Using Cool-Bottom Processing in RGB and AGB stars to explain Isotopic Ratios in Presolar Grains

Current stellar nucleosynthesis models fail to reproduce the measured isotopic abundances in group 2 oxygen-rich presolar grains, which are characterized by large ${}^{18}$O depletions. It was proposed that cool bottom processing in low-mass AGB stars is responsible for the observed isotopic abundances. We modeled cool-bottom processing during the RGB and the AGB of $1.2M_{\odot}$ stars to predict surface ${}^{18}$O/${}^{16}$O, ${}^{17}$O/${}^{16}$O, and ${}^{26}$Al/${}^{27}$Al ratios. Effective secular mixing must work against the steep mean molecular weight ($\mu$) gradient at the bottom of the radiative zone below the convective envelope to overcome a net increase in $\mu$ on the order of $0.01\%$ to recreate observed isotopic ratios. Sensitivity tests in which ${}^{18}$O$(p,\alpha){}^{15}$N and ${}^{16}$O$(p,\gamma){}^{17}$F were varied using reaction rate of factors of 10/0.1 and 1.4/0.71 respectively suggest that nuclear physics input is an important factor in model-grain comparison. This work shows that a secular cool-bottom mixing model that preserves stratification is a viable origin mechanism of the isotopic ratios observed in grains. We will also present an analysis of the surface ${}^{26}$Mg/${}^{24}$Mg, and ${}^{25}$Mg/${}^{24}$Mg ratios, $2M_{\odot}$ and $3M_{\odot}$ stars, and Monte Carlo impact studies on a range of reactions using current experimental uncertainties.

Speaker: Maeve Cockshutt (University of Victoria)

cockshuttPosterAbs167.pdf

153 Using slow ions in accelerator mass spectrometry for experimental nuclear astrophysics

Accelerator Mass Spectrometry (AMS) is the most sensitive technique for direct atom counting of many long-lived radionuclides. The addition of a buffer gas-filled ion cooler to the low-energy side of the AMS system opens up exciting new possibilities, especially in the mass range $60-200\,\mathrm{amu}$. The new ion cooler ILTIS, built at Helmholtz-Zentrum Dresden-Rossendorf in cooperation with the University of Vienna will be added to the new dedicated $1\,\mathrm{MV}$ AMS facility HAMSTER in Dresden. In the ion cooler, the near-thermal ion beam is collinearly overlapped with a laser beam to induce laser photodetachment ($A^– + \gamma \to A + e^-$). Using suitable molecules, this neutralizes any interfering atomic isobar while leaving the isotope of interest unaffected. Some radionuclides, whose detection has already been proven to benefit from this technique are e.g. ${}^{26}\mathrm{Al}$, ${}^{36}\mathrm{Cl}$, ${}^{90}\mathrm{Sr}$, ${}^{135}\mathrm{Cs}$ and ${}^{182}\mathrm{Hf}$. We will highlight the new measurement capabilities of ILTIS and give an outlook on AMS measurements of ${}^{90}\mathrm{Sr}$ and ${}^{135}\mathrm{Cs}$. AMS can provide direct assessments of the thermal and epithermal neutron capture cross sections on the radioactive target nuclei ${}^{134}\mathrm{Cs}$ and ${}^{89}\mathrm{Sr}$, leading to ${}^{135}\mathrm{Cs}$ ($T_{1/2} = 2.3\,\mathrm{Myr}$) and ${}^{90}\mathrm{Sr}$ ($28.91\,\mathrm{yr}$), respectively, which can serve as an anchor point for estimating the important cross sections in the astrophysical relevant keV-energy region.

Speaker: Alexander Wieser (Helmholtz-Zentrum Dresden-Rossendorf - Accelerator Mass Spectrometry and Isotope Research)

154 Variety of disk wind-driven explosions in massive rotating stars

At the end of its evolution, the collapse of a massive star's core into a proto-neutron star is the starting point for a complex sequence of events with many possible outcomes.
Specifically, very compact and rotating stars with a high mass ($M_*>16 \,M_\odot$), are likely to create a so-called ``failed core-collapse supernova'', forming a black hole surrounded by an accreting disk. It has been shown that the disk wind generated through viscous dissipation inside the disk may be the source of high energy ($E_\mathrm{expl}>10^{52}$ erg) supernovae with a high $^{56}$Ni mass (M$_{^{56}{Ni}}\ge 0.1\, M_\odot$).

In this scenario, the properties of the ejecta and the $^{56}$Ni production are strongly related to the wind injection from the accretion disk. In this talk, I will analyze these properties, investigating the impact of the disk mass and energy injected from the system on the final ejecta. I will focus on observational properties such as the explosion energy, the ejecta mass, and the $^{56}$Ni mass produced for different progenitor model. I will then show the strong correlation between the explosion energy and the ejecta mass, and compare our results for the $^{56}$Ni mass distribution with observational data.

Speaker: Ludovica Crosato Menegazzi (Max Planck Institute for Gravitational Physics)

91_Poster_CrosatoMenegazzi.pdf

155 Weak rates determining the production of the $^{205}$Pb cosmochronometer in AGB stars

$^{205}$Pb has been proposed as a cosmochronometer for the early solar system as it is only produced in the s-process and has a half-life of 17 My. This half-life can change dramatically in the stellar environment depending on the ionization stage of $^{205}$Pb and $^{205}$Tl and the thermal population of excited nuclear states. $^{205}$Pb has an excited 1/2$^-$ state at 2.3 keV that shortens its half-life by six orders of magnitude. On the other hand $^{205}$Pb can be produced by bound-state beta decay of highly ionized $^{205}$Tl. To reliably model the synthesis of $^{205}$Pb in AGB stars therefore requires a consistent treatment of both electron capture rates in $^{205}$Pb and bound-state beta decay rates in $^{205}$Tl for a wide range of temperatures and densities. Compared to previous work by Takahashi and Yokoi we could improve the rates by using an experimentally determined value for the bound-state beta decay of $^{205}$Tl that has been measured recently by the E121 collaboration at GSI. We also improved the description of the interaction between ions and plasma and used Dirac-Hartee-Fock calculations for the spectra and wave functions of the $^{205}$Pb and $^{205}$Tl ions.

Supported by the Deutsche Forschungsgemeinschaft – Project-ID 279384907 – SFB 1245.

Speaker: Thomas Neff (GSI Helmholtzzentrum für Schwerionenforschung, Germany)

NPA-Poster-Neff-88.pdf

NPA-PosterPitch-Neff-88.pdf

156 What is the Final Fate of Intermediate Mass Stars: Thermonuclear or Core-Collapse Supernova?

The fate of stars with intermediate mass ($\approx 7-11 \, M_\odot$) is still not certain. In their final stages, they develop degenerate oxygen-neon cores, potentially culminating in electron capture supernovae. Both a thermonuclear explosion, as well as a collapse to a neutron star are possible, critically depending on the oxygen ignition density. Understanding the oxygen ignition process is crucial to draw further conclusions and 3D hydrodynamical simulations are needed. In the late stages of evolution, forbidden electron captures, like the second forbidden transition between the ground states of ${}^{20}\mathrm{Ne}$ and ${}^{20}\mathrm{F}$, play a key role and significantly influence the density profile at the time of oxygen ignition. In addition, heating due to electron capture processes on ${}^{24}\mathrm{Mg}$ and ${}^{24}\mathrm{Na}$ leads to convectively unstable regions, which may not be correctly described in 1D stellar evolution codes like MESA. We aim to evaluate the impact of these convectively unstable regions and their impact on the later ignition of oxygen burning by employing the 3D hydrodynamical Seven-League Hydro code, while also considering the relevant electron capture rates.

Work supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) Project-ID MA 4248/3-1; RO 3676/7-1.

Speaker: Paul Christians (GSI Helmholtzzentrum für Schwerionenforschung)

Poster_75.pdf

157 Measurement of the $^{3}$He($\alpha,\gamma$)$^{7}$Be $\gamma$-ray angular distribution

The $^{3}$He($\alpha,\gamma$)$^{7}$Be reaction plays a significant role in Big Bang nucleosynthesis, as well as in stellar hydrogen burning. It affects the nucleosynthesis of primordial $^{7}$Li, as well as the theoretical prediction of solar $^{7}$Be and $^{8}$B neutrino fluxes.
A measurement of its $\gamma$-ray angular distribution was performed using the 5$\,$MV Pelletron accelerator at the Felsenkeller shallow-underground laboratory in Dresden. A $^4$He beam was used to irradiate solid $^3$He implanted targets. The prompt $\gamma$-rays were detected using more than 20 HPGe crystals surrounding the setup.
This contribution will report on experimental data in the energy range of $E_{cm} = 450 - 1220\,$keV, as well as its impact on S(0). Furthermore the results will be put into context of already existing data sets.

Speaker: Mr Peter Hempel (Helmholtz-Zentrum Dresden-Rossendorf)

158 Impact of ${}^{56}$Ni production in neutrino-driven winds from long-lived binary neutron star merger remnants

We investigate the nucleosynthesis and kilonova light curve based on recent long-term binary neutron star merger simulations that incorporate a two-moment neutrino-transport scheme. The ejecta are evolved for 30 days using axisymmetric radiation-hydrodynamics simulations coupled in-situ to a complete nuclear network. For the first time, we find that the neutrino-driven wind from the post-merger remnant is mostly proton-rich. The resulting nucleosynthesis products are predominantly ${}^{56}$Ni and other iron-group elements. After a few days, the decay of ${}^{56}$Ni and later ${}^{56}$Co becomes the primary source of heating in the expanding matter, which significantly alters the time dependence of the kilonova light curve. The observation of this effect would be a smoking gun for the presence of a long-lived neutron-star remnant in future kilonova observations.

Speaker: Maximilian Jacobi (University of Jena)

Tuesday 17 September

Plenary Session: E: Explosive processes (1).

Convener: Anton Wallner (HZDR)

159 Stellar nucleosynthesis in explosive environments

Explosive stellar environments such as novae, supernovae, x-ray bursts and neutron star mergers have been identified as possible candidate sites where the majority of the heavy elements are synthesized. Understanding the underlying mechanisms of the explosions can help to shed light on the observed chemical abundances at these sites. Accurate theoretical models of these environments can be used to compare with astronomical observations to gain insight in the underlying physics. Many of these stellar models suffer from large uncertainties in nuclear physics inputs such as nuclear masses, half-lives and reaction rates. Several highlights of experimental efforts from the nuclear physics community to constrain these uncertainties will be presented.

Speaker: Heshani Jayatissa (Los Alamos National Laboratory)

0900_HJ_NPA2024.pdf

160 Insight to the Explosion Mechanism of Core Collapse Supernovae Through $\gamma$-ray Spectroscopy of ${}^{46}$Cr

Currently, the explanation behind the explosion mechanism of core collapse supernovae is yet to be fully understood. New insight to this phenomena may come through observations of $^{44}$Ti cosmic $\gamma$ rays; this technique compares the observed flux of cosmic $^{44}$Ti $\gamma$ rays to that predicted by state-of-the-art models of supernova explosions. In doing so, the mass cut point of the star can be found. However, a road block in this procedure comes from a lack of precision in the nuclear reactions that destroy $^{44}$Ti in supernovae, most notably the reactions $^{44}$Ti$(\alpha,p)^{47}$V and $^{45}$V$(p,\gamma)^{46}$Cr. Therefore, this study aims to better understand the $^{45}$V$(p,\gamma)^{46}$Cr reaction by performing $\gamma$-ray spectroscopy of $^{46}$Cr with the aim of identifying proton-unbound resonant states.

The experiment was conducted at the ATLAS facility at Argonne National Laboratory, using the GRETINA+FMA setup, where $^{46}$Cr was produced via the fusion-evaporation reaction $^{12}$C($^{36}$Ar,2$n$). The cross section for producing $^{46}$Cr, in this reaction, is estimated to be in the $\mu$b range. Nevertheless, with the power of the GRETINA+FMA setup, we show that it is possible to cleanly identify $\gamma$ rays in $^{46}$Cr. These include decays from previously unidentified states above the proton-emission threshold, corresponding to resonances in the $^{45}\mathrm{V} + p$ system.

Speaker: Chris Cousins (University of Surrey)

0925_Cousins.pdf

161 Electron-capture supernovae - Thermonuclear explosion or gravitational collapse? - The fate of sAGB stars on a knife's edge

New models of so-called electron-capture supernovae (ECSNe) suggest that while the full collapse of sAGB stars to a NS is still a possibility, the energy release by the electron-capture reactions can also trigger a thermonuclear runaway initiating explosive thermonuclear burning in a ''thermonuclear ECSN'' (tECSN).
Initial studies suggest that tECSNe could reproduce the solar abundances of so far problematic isotopes such as $^{48}$Ca, $^{50}$Ti, $^{54}$Cr, together with $^{58}$Fe, $^{64}$Ni, $^{82}$Se, and $^{86}$Kr as well as several Zn-Zr isotopes, without introducing new tensions with the solar abundance distribution.
In this work, we heavily expand on the existing tECSNe models, exploring a multitude initial conditions and ignition geometries.
Our initial results suggest that the critical central density below which the collapse can be halted by thermonuclear burning is somewhere between $10.15 < \log \rho_c^\mathrm{ini} < 10.3$ depending on the ignition geometry.
We additionally provide a comprehensive set of nucleosynthesis yields for our tECSN models and investigate the dependency of our results on the used rates.
These results will be used as an input for our 3D radiative transfer simulations, contributing the first-of-its-kind synthetic observables which will allow us to determine the feasibility of tECSNe as a realistic supernova scenario.

Speaker: Alexander Holas (Heidelberg Institute for Theoretical Studies)

NPIA-XI_Presentation_GIF_version.pptx

162 Unraveling the Influence of Magnetic Fields on the Nucleosynthesis in Magnetorotational Supernovae

Magnetorotational supernovae are hypothesized as environments for the rapid neutron-capture process (r-process) responsible for the formation of heavy elements in our Universe. The magnetic fields within these events are a key ingredient in this process, yet their precise strength and configuration remain elusive. To address this, we analyzed comprehensive 3D MHD supernova simulations with sophisticated neutrino transport, exploring the impact of both magnetic field strength and topology on the nucleosynthesis. Our findings highlight the critical role not only of magnetic field strength but also of topology in the synthesis of heavy elements. Significantly, our study encompasses a range of magnetic field configurations beyond the conventional aligned large-scale dipole, revealing that the r-process occurs solely under the aligned large-scale dipole scenario. Moreover, we demonstrate the robustness of this result against nuclear physics uncertainties, such as nuclear masses and beta decays. Notably, all calculations were executed utilizing the state-of-the-art single-zone nucleosynthesis network WinNet, recently released as open-source software.

Speaker: Moritz Reichert (University of Valencia)

MReichert_NPA_talk.pptx

163 Uncertainties in explosive nucleosynthesis in core-collapse supernovae from Monte Carlo variation of reaction rates

Massive stars (>10M_☉) undergo core-collapse supernova explosions at the end of evolution. These explosions release elements ranging from helium (produced during the stellar evolution) to iron peak synthesized in explosive nucleosynthesis. Although the explosion mechanism of core-collapse supernovae is not fully understood, 1D spherically symmetric explosion models have been constructed that relatively well reproduce the observed elemental abundances. Such models are ideal to systematically study the impact of nuclear reaction rates on the nucleosynthesis. Some of the nuclear reactions in explosive nucleosynthesis, can be accessed through accelerator experiments.

We have developed a nucleosynthesis code with Monte-Carlo framework that accounts for nuclear reaction uncertainties and applied it to processes beyond iron. Given its general applicability, our framework is naturally suited for studying supernova explosive nucleosynthesis. In this study, we investigate 1D explosion models using the "PUSH" method, which simulates explosions by mimicking the enhanced neutrino heating observed in multi-dimensional simulations. We focus on nucleosynthesis in progenitors with solar and sub-solar metallicity around M_ZAMS=16 M_☉. Detailed post-process nucleosynthesis calculations with Monte Carlo analysis is employed to comprehensively explore the effects of uncertainties in relevant reaction rates. Additionally, we identify "key reaction rates", based on statistical analysis of our Monte Carlo results.

Speaker: Nobuya Nishimura (The University of Tokyo)

n_nishimura.pdf

164 Simulations of thermonuclear astrophysical transients

Astrophysical thermonuclear explosions typically arise from interactions in binary star systems. Their predicted observational characteristics span a wide range in parameter space and include Type Ia supernovae, as well as other classes of transient events. Understanding and interpreting the rich set of new data expected from upcoming transient searches requires advances in modelling the underlying events. I discuss approaches to simulating thermonuclear explosions arising from various scenarios in detailed three-dimensional (magneto-)hydrodynamic models. Improvements in numerical methods allow us to constrain the explosion physics and progressively enable us to study the initiation of the explosions from the dynamics of the progenitor system. These three-dimensional explosion models then serve as an input to nucleosynthesis and radiative transfer calculations, from which implications for observables can be derived. I will give an overview of recent simulations and discuss how such approaches can help understand the enigmatic nature of Type Ia supernovae but also guide the modeling of the zoo of newly observed transient events.

Speaker: Friedrich Roepke (Heidelberg University / HITS)

Poster Flashes: E

Every poster presenter has 1 minutes to present 1 slide summarizing the poster

165 Dipole strength in the well-deformed nucleus ${}^{154}$Sm in the Pygmy Resonance energy-region via $(\gamma,\gamma^\prime)$ reactions

The E1 $\gamma$-ray strengh of the Pygmy Dipole Resonance (PDR), close to the neutron threshold on the top of the low-energy tail of the Isovector Giant Dipole Resonance (IVGDR), exhausting only few percent of the TRK sum rule is known to affect significantly the radiative neutron capture cross section calculations of the astrophysical r-process [1] which is responsible for the nucleosynthesis of heavy neutron-rich nuclei in the universe.

So far, the PDR strength distribution has been measured in several neutron-rich nuclei [2,3], mostly on or near neutron shell closures, where the shape is (quasi) spherical. The systematic summed strengths in an isotopic and isotonic chains of the nuclear chart, seems to be linked to the neutron excess.

Although described in various microscopic and hydrodynamic theoretical models as oscillations of the neutron excess against an isospin neutral core, the nuclear structure (collective and/or singular character) of the PDR states and the strength fragmentation are still controverse.

The corresponding neutron-skin size, related to the (a)symmetry energy term is an important ingredient for the equation of state modeling the neutron stars.

Since the rised interest of the PDR strength as well from astrophysical as nuclear structure point of view and in order to complement our experimental database, one need to explore the case of deformed shapes where such information is limited to only a very few cases, as for ${}^{156}$Gd [4] and ${}^{164}$Dy [5]. In this talk, I will present our recent results on the well-deformed ${}^{154}$Sm ($\beta=0.34$) which we investigated via the ${}^{154}$Sm$(\gamma,\gamma^\prime)$ reactions up to the neutron-separation threshold $S_n = 7.97\,\mathrm{MeV}$, using the bremsstrahlung facility [6] at ELBE supra-conductor accelerator of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Germany, producing an electron beam of energy of $9.5\,\mathrm{MeV}$. An evidence for PDR strength have been observed which will be compared to the spherical isotope ${}^{144}$Sm at $N=82$ closed neutron shell and to the ${}^{156}$Gd isotone.

[1] S. Goriely, et al., Nucl. Phys. A 739 (2004) 331.
[2] D. Savran, et al., Prog. Part. Nucl. Phys. 70 (2013) 210.
[3] A. Bracco, et al., Eur. Phys. J. A 55 (2019) 233.
[4] M. Tamkas et al., Nuclear Physics A 987 (2019) 79
[5] O. Papst et al., Phys. Rev. C 87, 102, (2020) 034323
[6] R. Schwengner et al., Nucl. Instrum. Methods A 555 (2005) 211

Speaker: Dr Nadia Benouaret (University of Science and Technology Houari Boumediene (USTHB))

176_300_Pitch.pdf

166 Using Cool-Bottom Processing in RGB and AGB stars to explain Isotopic Ratios in Presolar Grains

Current stellar nucleosynthesis models fail to reproduce the measured isotopic abundances in group 2 oxygen-rich presolar grains, which are characterized by large ${}^{18}$O depletions. It was proposed that cool bottom processing in low-mass AGB stars is responsible for the observed isotopic abundances. We modeled cool-bottom processing during the RGB and the AGB of $1.2M_{\odot}$ stars to predict surface ${}^{18}$O/${}^{16}$O, ${}^{17}$O/${}^{16}$O, and ${}^{26}$Al/${}^{27}$Al ratios. Effective secular mixing must work against the steep mean molecular weight ($\mu$) gradient at the bottom of the radiative zone below the convective envelope to overcome a net increase in $\mu$ on the order of $0.01\%$ to recreate observed isotopic ratios. Sensitivity tests in which ${}^{18}$O$(p,\alpha){}^{15}$N and ${}^{16}$O$(p,\gamma){}^{17}$F were varied using reaction rate of factors of 10/0.1 and 1.4/0.71 respectively suggest that nuclear physics input is an important factor in model-grain comparison. This work shows that a secular cool-bottom mixing model that preserves stratification is a viable origin mechanism of the isotopic ratios observed in grains. We will also present an analysis of the surface ${}^{26}$Mg/${}^{24}$Mg, and ${}^{25}$Mg/${}^{24}$Mg ratios, $2M_{\odot}$ and $3M_{\odot}$ stars, and Monte Carlo impact studies on a range of reactions using current experimental uncertainties.

Speaker: Maeve Cockshutt (University of Victoria)

cockshuttPosterSlideAbs167.pdf

167 The $^{140}$Ce(n,$\gamma$) cross section measured at n_TOF and its astrophysical implications

The slow (s) and rapid (r) neutron-capture processes are major producers of elements heavier than iron. The main component of the s-process takes place in low-mass AGB stars, through a series of neutron capture reactions and beta decays, resulting in a flow that proceeds along the beta-stability valley. In this context, the neutron-capture cross sections of closed neutron shell nuclei represent bottlenecks for the s-process. Among them, $^{140}$Ce is particularly interesting because of a discrepancy between stellar model predictions and observations of stars belonging to the Globular Cluster M22. This discrepancy triggered the n_TOF collaboration to measure the $^{140}$Ce neutron capture cross section in a wide neutron energy range at the n_TOF facility, combined with a highly enriched $^{140}$Ce sample and an experimental setup based on four low neutron sensitivity liquid scintillations detectors. The high accuracy, high-resolution data of n_TOF have led to a Maxwellian Averaged Cross Sections (MACS) with an uncertainty better than 5%. At low energy, the new value is up to 40% larger than the available library evaluations. This new value, however, did not solve the existing discrepancy, possibly indicating the presence of additional nucleosynthesis processes. I will present the n_TOF measurement and its astrophysical implications.

Speaker: Dr Rudra N. Sahoo (INFN Sezione di Bologna)

113_261_Pitch.pdf

168 The i-process in AGB stars with Overshoot

The production of neutron-rich elements at neutron densities intermediate to those of the s- and r-processes, the so-called i-process, has been identified as possibly being responsible for the observed abundance pattern found in CEMP-r/s stars. The production site may be low-metallicity stars on the Asymptotic Giant Branch where the physical processes during the thermal pulses are not well known. In this talk I will present models of a 1.2 M⊙ , Z=5 × 10−5 star, exploring the impact of overshoot parameters on proton ingestion events (PIEs) and the neutron densities as a necessary precondition for the i-process. In addition, light element abundances in our models can be leveraged to favor certain sets of overshoot parameters.

Speaker: Bryce Remple (Max-Planck-Institut fuer Astrophysik)

PosterPitch.pdf

169 The 12C+12C reaction at the Bellotti Ion Beam Facility - The setup development

The 12C+12C fusion reaction plays an significant role in our understanding of heavy element nucleosynthesis, as well as supernovae of type Ia. Two of its channels, namely $^{12}$C($^{12}$C,p)$^{23}$Na and $^{12}$C($^{12}$C,$\alpha$)$^{20}$Ne are currently under study at the Bellotti Ion Beam Facility within an energy range from 2$\,$MeV to 3.5$\,$MeV. While the first phase is focussing on 2.0$\,$MeV to 2.2$\,$MeV, where there is no direct measurement as of today, future upgrades will try to cover the entire Gamow window.
The experimental approach is based on water-cooled, solid graphite targets, as well as a 150% HPGe detector and a segmented NaI detector in close geometry surrounded by a massive lead castle. This contribution will report on the development of the experimental setup, as well as on a dedicated target study, which was done at the Felsenkeller shallow-underground laboratory in Dresden.

Speaker: Dr Steffen Turkat (Università di Padova)

181_302_Pitch.pdf

170 Exploring Supernova signatures in time-resolved records from the Atacama Desert, Chile

The detection of cosmic signatures in deep-sea, ice, and lunar samples has made an important contribution to nuclear astrophysics in recent years. In particular, ${}^{60}$Fe from near-Earth supernovae has been imprinted during the time periods $2-3$ and $7-8\,\mathrm{Myr}$ ago.

This data corroborates theoretical studies that suggest that more than $10$ SNe exploded at a distance of $50-150\,\mathrm{pc}$ over the last $10-15\,\mathrm{Myr}$. Their overriding shock fronts created a volume of hot gas that is seen in observational data and referred to as the 'Local Bubble', which currently engulfs our Solar System.

We here explore for the first time sedimentary records on land, in particular from the oldest and driest desert on Earth; the Atacama Desert, Chile. In contrast to previous archives, Atacama Desert deposits are easily accessible, reach more than $10\,\mathrm{Myr}$ into the past and are not affected by continuous aqueous diffusion.

The low sedimentation rates in the Atacama Desert that are similar to deep-sea sediments, as well as the hyper-arid conditions facilitate the preservation of cosmic traces over millions of years, bearing the potential for the detection of individual supernovae within each of the broad signals.

Speaker: Jenny Feige (Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung)

185_305_Pitch.pdf

171 Early onset of color-superconducting quark matter in neutron stars

We present a relativistic density functional approach to color superconducting quark matter that mimics quark confinement by a fast growth of the quasiparticle self-energy in the confining region. The approach is shown to be equivalent to a chiral model of quark matter with medium dependent couplings. The approach to the conformal limit at asymptotically high densities is provided by a medium dependence of the vector-isoscalar, vector-isovector and diquark couplings motivated by non-perturbative gluon exchange [2]. While the (pseudo)scalar, vector-isoscalar and vector-isovector sectors of the model are fitted to the mesonic mass spectrum and vacuum phenomenology of QCD, the strength of interaction in the diquark channel is varied in order to obtain the best agreement with the observational constraints from measurements of mass, radius and tidal deformability of neutron stars. These constraints favor an early onset of deconfinement and color superconductivity in neutron stars with masses below one solar mass. We also discuss a new two-zone interpolation scheme for the construction of the hadron-to-quark matter transition [3] that allows to test different structures of the QCD phase diagram with one, two or no critical endpoints in simulations of supernova explosions, neutron star mergers and heavy-ion collisions. I argue that the formation of color-superconducting quark matter drives the trajectories of its evolution in supernovae and neutron star mergers towards the regimes reached in terrestrial experiments with relativistic heavy ion collisions.

[1] O. Ivanytskyi and D. Blaschke, Phys. Rev. D 105, 114042 (2022)
[2] O. Ivanytskyi and D. Blaschke, Particles 5, 514 (2022)
[3] O. Ivanytskyi and D. Blaschke, Eur. Phys. J A. 58, 152 (2022

Speaker: Oleksii Ivanytskyi (University of Wroclaw)

Ivanytskyi191_pitch.pdf

172 Investigation of excited states in $^{15}$O at AGATA and Felsenkeller

The CNO cycle plays a key role in the nucleosynthesis of massive stars and their energy production. The $^{14}\mathrm{N}(\mathrm{p},\gamma){}^{15}\mathrm{O}$ reaction is the slowest in this cycle and, therefore, controls the speed of the entire cycle, influencing the synthesis of carbon, nitrogen, oxygen and fluorine. However, investigating the reaction at astrophysically relevant energies is challenging. The total reaction rate is dominated by two resonances: at $E_\mathrm{r}=259\,\mathrm{keV}$ and at $E_\mathrm{r} =-504\,\mathrm{keV}$.

While the first resonance is well understood, the impact of the subtreshold state on the $^{14}\mathrm{N}(\mathrm{p},\gamma){}^{15}\mathrm{O}$ reaction remains unclear and difficult to measure experimentally. In this work, we focus on investigating the lifetime, sub-fs range, of the $E_x = 6.793\,\mathrm{MeV}$ state in $^{15}\mathrm{O}$ to constrain the response width and therefore, its impact on the $^{14}\mathrm{N}(\mathrm{p},\gamma){}^{15}\mathrm{O}$ reaction. The experimental study was conducted in two separate campaigns at the Legnaro National Institute for Nuclear Physics in Italy (INFN), using the AGATA+SAURON array, and at the shallow-underground Felsenkeller laboratory in Germany. The Felsenkeller measurements were performed using $14.5\,\mathrm{MeV}$ and $16.9\,\mathrm{MeV}$ oxygen beams provided by the external source, which impinged on $^3$He targets. A description of the setup, target stability tests, and preliminary analysis of both campaigns will be presented.

Speaker: Max Osswald (Helmholtz Zentrum Dresden Rossendorf)

314_315_Pitch.pdf

10:50 Coffee Break

173 Welcome by the Prorector of TU Dresden

Speaker: Prof. Michael Kobel (TU Dresden)

Plenary Session: F: New tools and techniques (2). & Big Bang Nucleosynthesis (1).

Convener: David Blaschke

174 The Compton Spectrometer and Imager: Science Goals and Mission Status

The Compton Spectrometer and Imager (COSI) is a NASA Small Explorer (SMEX) satellite mission with a planned launch in 2027. COSI operates in the $0.2-5\,\mathrm{MeV}$ gamma-ray bandpass and obtains coverage of the entire sky every day. COSI provides imaging, spectroscopy, and polarimetry of astrophysical sources, and its germanium detectors have excellent energy resolution for emission line measurements. COSI science includes four main topics: 1. mapping radioactive elements from nucleosynthesis; 2. studying $511\,\mathrm{keV}$ emission from antimatter annihilation in the Galaxy; 3. making polarization measurements of accreting black holes; and 4. detecting and localizing gamma-ray bursts. In this presentation, I will discuss the scientific advances expected from COSI related to gamma-ray lines, including studies of ${}^{26}$Al and ${}^{60}$Fe emission from massive star clusters in the Galaxy as well as $^{44}$Ti from young supernova remnants. I will describe how COSI's measurements of $511\,\mathrm{keV}$ emission will give new information about positron production on Galactic scales. In addition, I will provide a description of the COSI instrument as well as an update on the overall mission.

Speaker: John Tomsick (University of California, Berkeley)

Tomsick_COSI_NPAXI_v2a.pdf

175 The German Center for Astrophysics (DZA)

The German Center for Astrophysics aims to generate knowledge and advance innovations in order to continue to position Germany at the forefront of astrophysics. It relies on broad international cooperation and strives to secure technological sovereignty through the development of new technologies and the transfer of knowledge. A particular focus is on promoting environmentally friendly digitalization by combining data streams from astronomical observatories and developing resource-saving computing methods. The center takes a holistic approach that aims not only at research and innovation, but also at the exchange of knowledge and the promotion of young talent. It strives to inspire young people for science and technology and to create long-term prospects for them in the region. At the same time, the center is to be established as a center with international appeal that promotes structural change in Lusatia and contributes to the formation of identity in the region.

Speaker: Prof. Günther Hasinger (Deutsches Zentrum für Astrophysik)

176 Reactions with stored nuclei with CARME@CRYRING

Heavy ion storage rings have been used for nuclear astrophysics measurements for decades, and have proven themselves powerful tools for exotic mass measurements.

Recent advances in ring operation and beam intensities made measurement of nuclear reactions at rings possible. In particular, pioneering measurements were carried out at the ESR at GSI (Germany) investigating the astrophysical p-process.

The recent commissioning of a new low-energy heavy ion storage ring at GSI/FAIR - the CRYRING - opened the door to the possibility to carry out measurements at rings directly at the energies of interest for quiescent burning scenarios, as well as nova and supernova explosions. CRYRING is the only low-energy ring in the world to be linked to a radioactive beam facility (FAIR), and offers unique new possibilities.

In this talk I will describe the CRYRING Array for Reaction MEasurements (CARME) which was designed to carry out nuclear reaction measurements in the extreme high vacuum environment of the CRYRING. I will show commissioning results and future science plans. The programme at CARME is supported by the ELDAR ERC grant.

Speaker: Carlo Bruno (The University of Edinburgh)

177 The study of the $^7$Li(γ,α)$^3$H reaction at energies below 6 MeV at HIγS

The abundances of the light elements can be spectroscopically determined by observing the low-metallicity stars. Usually, those measurements are in agreement with the Big Bang Nucleosynthesis predictions. Particularly, the Li-7 measured abundance is 3-4 times lower than expected, discrepancy known as the “cosmological Li problem”. The reaction $^3$H(α,γ)$^7$Li contributes to the production of Li-7 in Universe and can be studied through its inverse reaction, according to the reciprocity theorem. In consequence, the Li-7 photodisintegration has been measured by our team in 2017 at the High Intensity γ-ray Source (HIγS) Laboratory of Duke University (USA) using a silicon detector array (SIDAR) to observe the coincidences between the alpha particles and the tritons. The considered energies of the gamma beam have been between 4.4 and 10 MeV, but below 6 MeV the coincidences have been observed only in the thinner detectors. In 2023, a new similar experimental campaign, with an improved set-up, took place at HIγS for gamma-beam energies between 3.7 and 6 MeV. The coincidences have been clearly separated and the preliminary astrophysical S-factor of the direct $^3$H(α,γ)$^7$Li reaction has been successfully extracted.
The set-up and the preliminary results of the experimental campaign performed at HIγS in 2023 will be presented.

Speaker: Ms Ioana Kuncser (Extrem Light Infrastructure - Nuclear Physics / IFIN-HH & POLITEHNICA Bucharest National University for Science and Technology)

Kuncser_Ioana_NPA.pdf

Kuncser_Ioana_NPA.pptx

178 Measurement of the $^{3}$He($\alpha,\gamma$)$^{7}$Be $\gamma$-ray angular distribution

The $^{3}$He($\alpha,\gamma$)$^{7}$Be reaction plays a significant role in Big Bang nucleosynthesis, as well as in stellar hydrogen burning. It affects the nucleosynthesis of primordial $^{7}$Li, as well as the theoretical prediction of solar $^{7}$Be and $^{8}$B neutrino fluxes.
A measurement of its $\gamma$-ray angular distribution was performed using the 5$\,$MV Pelletron accelerator at the Felsenkeller shallow-underground laboratory in Dresden. A $^4$He beam was used to irradiate solid $^3$He implanted targets. The prompt $\gamma$-rays were detected using more than 20 HPGe crystals surrounding the setup.
This contribution will report on experimental data in the energy range of $E_{cm} = 450 - 1220\,$keV, as well as its impact on S(0). Furthermore the results will be put into context of already existing data sets.

Speaker: Dr Steffen Turkat (Università di Padova)

13:05 Lunch Break

Plenary Session: G: Cosmochemistry and Galactic Chemical Evolution (1).

Convener: Günther Hasinger (Deutsches Zentrum für Astrophysik)

179 Signatures of stellar nucleosynthesis in meteorites

Meteorites, also known as the poor scientists' space probe, are valuable samples to study the solar nebula and its constituents. Certain primitive meteorites captured the composition of the solar system and have not been altered in the 4.5 billion years since its formation. These rocks also carry nucleosynthetic anomalies that allow us to deduce stellar processes in the solar neighborhood prior to solar system formation. In addition, primitive meteorites contain small presolar grains, i.e., bona-fide dust particles that condensed in the outflow and ejecta of dying stars and captured the nucleosynthetic fingerprint of their formation environment. These samples allow us to directly probe stellar nucleosynthesis and galactic chemical evolution of isotopes with high precision and thus allow us to constrain our theoretical understanding of these events and the underlying nuclear physics.

In my talk I will present an overview on how meteorite and presolar grain measurements allow us to decipher astrophysical processes. I will specifically present measurements that allow us to constrain rare processes that cannot be otherwise observed in nature, e.g., the formation and galactic chemical evolution of proton- and neutron-rich isotopes.

Speaker: Reto Trappitsch (EPFL)

NPA_XI_slides_trappitsch.pdf

180 Impact of Stellar Yields on Galactic Chemical Evolution

The chemical enrichment history of the elements observed in the Sun and in other stars is providing crucial information about the formation and the chemical evolution of the Milky Way. The production of specific elemental ratios and isotopes can be used to constrain different uncertainties affecting galactic chemical evolution (GCE) simulations. Theoretical stellar yields are one of the major uncertainties affecting GCE, as it is consistently reported across the literature.

In this talk I will present different cases where GCE have been used to directly test stellar yields, and even verify the impact of specific uncertainties affecting stellar nucleosynthesis products, like nuclear reaction rates and stellar models. Elements, isotopes and even several radioactive isotopes can be used for this purpose. Solar abundances provide a crucial benchmark for GCE. Isotopic ratios in presolar grains, signatures of radioactive isotopes from the Early Solar System material and elemental abundances of other stars also provide critical information for GCE theoretical calculations.

Speaker: Marco Pignatari (Konkoly Observatory, CSFK HUN-REN)

marco_dresden_2024_v2.pdf

181 Galactic chemical Evolution with short lived radioactive isotopes

Studying the galactic chemical evolution with short lived radioisotopes (SLRs) has a significant advantage over using stable elements: Due to their radioactive decay, SLRs carry additional timing information on astrophysical nucleosynthesis sites.

We can use meteoritic abundance data in conjunction with a chemical evolution model to constrain the physical conditions in the last rapid neutron capture process event that polluted the early Solar system prior to its formation [1].

Further, with the help of detections of live SLRs of cosmic origin in the deep sea crust [2], we can use these data in a 3-dimensional chemical evolution code to explain why different classes of radioisotopes should often arrive conjointly on Earth, even if they were produced in different sites (e.g., neutron star mergers, core-collapse/thermonuclear supernovae) [3].

Finally, we included radioisotope production into a cosmological zoom-in simulation to create a map of Al-26 indicating areas of ongoing star formation in the Galaxy, consistent with the observations by the SPI/INTEGRAL instrument[4]. We provide predictions for future gamma-ray detection instruments.

References:
[1] Côté et al., 2021 Science 371, 945
[2] Wallner et al., 2021 Science 372, 742W
[3] Wehmeyer et al., 2023 ApJ 944, 121
[4] Kretschmer et al., 2013 A&A 559, A9

Speaker: Benjamin Wehmeyer (University of Wroclaw)

182 Search for neutron stars from the supernovae that delivered 60-Fe to Earth to constrain supernova nucleosynthesis

60-Fe found in the Earth crust points to one or several core-collapse supernovae within 100-150 pc of Earth 1.5-2.5 Myr ago, probably from the young OB-associations in Scorpius, Centaurus, and Lupus.

We search for neutron stars formed in those supernovae: (i) We trace back the motion of all young neutron stars and runaway stars (whose former common multiple star system was disrupted by the supernova) to find cases where both were at the same place at the same time, as evidence for a supernova in a multiple star. This constrains time and distance towards the supernova and the mass of the progenitor star. We found one credible case: the pulsar PSR1706 and the runaway star zeta Oph (Neuhaeuser et al. 2020 MNRAS).

(ii) We also search for young nearby high-mass X-ray binaries consisting of at least one massive (OB) star and one compact object (usually a neutron star) in a close orbit to produce accretion and X-ray emission (PhD thesis K.-U. Michel).

We will present new results (i) and first results from (ii). Once distances and times of supernovae (and the supernova progenitor masses) that delivered 60-Fe to Earth are
determined, supernova nucleosynthesis models can be constrained.

Speaker: Mr Kai-Uwe Michel (AIU Jena)

NPA2024_Michel.pdf

15:35 Group Photo

15:40 Coffee Break

Plenary Session: H: Neutron capture processes (3).

Convener: Raphael Hirschi (Keele University)

183 Nuclear Model and Parameter Uncertainties on Nucleosynthesis: Insights into the i-Process in Early AGB Stars and r-Process in Neutron Star Mergers

Using a consistent statistical approach through the Backward-Forward Monte-Carlo method, we investigate both the parameter (statistic) and model (systematic) uncertainties associated with theoretical nuclear reaction rates of relevance during the i-process, and with theoretical nuclear masses of relevance during the r-process.

• For the i-process, we explore the impact on the i-process elemental production, and subsequently on the surface enrichment, for low-mass low-metallicity stars during the early AGB phase.
• For the r-process, we show the impact on the r-process production during Neutron Star Merger events.

These studies allow us to quantify the relative importance of parameters versus model uncertainties with respect to the surface abundances in AGB stars and to the r-process production during Neutron Star mergers.

We identify and provide a list of important reaction rates that would need to be better constrained in the future in order to improve our understanding of the i-process. We identify similarly important nuclear masses in the r-process production.

Speaker: Sébastien Martinet (Université Libre de Bruxelles)

NPA r-pro_i-pro-2.pdf

184 Origin of the heavy elements

In 2017, a multimessenger era started with the first gravitational wave detection from the merger of two neutron stars (GW170817) and the rich electromagnetic follow-up. The most exciting electromagnetic counterpart was the kilonova. The neutron-rich material ejected during the neutron star merger undergoes an r-process that produces heavy elements and a kilonova. Moreover, observations of abundances from the oldest stars reveal an additional r-process contribution of a rare and fast event, which could be core-collapse supernovae with strong magnetic fields, so called magneto-rotational supernovae. We combine hydrodynamic simulations of neutron star mergers and supernovae including state-of-the-art microphysics, with nucleosynthesis calculations involving extreme neutron-rich nuclei, and forefront observations of stellar abundances in the Milky Way and in orbiting dwarf galaxies. This opens up a new frontier to use the freshly synthesized elements to benchmark simulations against observations. The nucleosynthesis depends on astrophysical conditions (e.g., mass of the neutron stars) and on the microphysics included (equation of state and neutrino interactions). Therefore, comparing calculated abundances based on simulations to observations of the oldest stars and future kilonovae will lead to ground-breaking discoveries for supernovae, mergers, the extreme physics involved, and the origin of heavy elements.

Speaker: Almudena Arcones (TU Darmstadt)

Arcones.pdf

185 The R-Process Alliance: Hunting for Gold (or, maybe just, uranium)

Heavy elements like gold and uranium are produced via the rapid neutron-capture (r-)process. This process only occurs in rare explosive events in the Universe, like supernovae and neutron star mergers, making it highly challenging for astronomers to gather direct observations of the element creation. Likewise, it is difficult for nuclear physicists to recreate and study the nuclear process in the laboratory. These obstacles are why we today, more than six decades after the theoretical prediction of the r-process, still don't fully understand how and where gold and silver are made in the Universe. However, in 2017, the R-Process Alliance (RPA) initiated a successful new search to uncover bright metal-poor stars enriched with r-process elements. These stars are invaluable laboratories for studying the r-process as the gas from which these stars formed was polluted by at most a few enrichment events --- perhaps even a single explosion. The RPA has collected spectra of $\sim 2000$ stars and discovered over 70 new highly r-process-enhanced stars. I will report recent results from the RPA efforts, including evidence for the formation of super-heavy elements formed during the r-process and abundances from new Hubble Space Telescope observations.

Speaker: Terese Hansen (Stockholm University)

THansen.pdf

186 New half-lives measurements for r-process in A$\sim$225 Po-Fr nuclei

The astrophysical rapid-neutron capture process (r-process) of explosive nucleosynthesis is responsible for the formation of half of the heavy nuclei above Fe. Actinides are produced towards the end of this process, when the neutron flux is expected to be minimal, and it is supported also by fission processes. Given that the r-process path runs far away from the accessible species, in this heavy region of the chart of nuclides, experimental inputs on $\beta$ decay for nuclei beyond $N = 126$ are useful to test global nuclear models.

In this paper results from an experiment performed at GSI-FAIR within the HISPEC-DESPEC Phase-0 experimental campaign will be discussed. $220 < A < 230$ Po-Fr nuclei were populated in a relativistic fragmentation reaction induced by a $1\,\mathrm{GeV}$ ${}^{238}\mathrm{U}$ beam. The species were selected and identified using the FRagment Separator and implanted in the DEcay SPECtroscopy station to study their $\beta$ decay. The DESPEC station is composed of Double Sided Silicon-Strip Detectors sandwiched between two plastic scintillators, surrounded by a $\gamma$-detection array of HPGe and LaBr$_3$(Ce) detectors.

The extracted $\beta$-decay half-lives are discussed with recent theoretical models, to assess the impact of the measured values in the r-process predictions. Perspectives of future measurements in the region will be provided.

Speaker: Marta Polettini (University of Padova and INFN Padova)

187 The astrophysical ${}^{140}$Ce(n,$\gamma$)${}^{141}$Ce reaction: present and future

The ${}^{140}$Ce(n,$\gamma$)${}^{141}$Ce is recognized as an important reaction in the flow of neutron-capture nucleosynthesis due to the neutron-magic character of ${}^{140}$Ce and a corresponding small neutron capture cross section. We present here [1] measurements of the neutron-capture Maxwellian-averaged cross section (MACS) of stable cerium isotopes performed by activation in the quasi-Maxwellian ${}^{7}$Li(p,n) neutron field ($kT \sim 34\,\mathrm{keV}$) produced by the Liquid-Lithium Target (LiLiT) at Soreq Applied Research Accelerator Facility (SARAF). The MACS values ($kT= 30\,\mathrm{keV}$) are generally consistent with previous measurements and for ${}^{140}$Ce smaller by approximately 15-20%. In contrast a recent study of the ${}^{140}$Ce(n,$\gamma$)${}^{141}$Ce cross section measured via time of flight [2] leads to MACS values larger by ~20-40% than quoted in the experimental database KADoNIS [3] in the $kT \sim 5-10\,\mathrm{keV}$ (see also [4]). We note here that the the activation and time-of-flight experiments were focused on different $kT$ regions ($\sim 30\,\mathrm{keV}$ and $\sim 10\,\mathrm{keV}$, respectively), possibly affecting the MACS determinations for $kT$ values out of their respective regions. In order to contribute to the understanding of neutron-capture nucleosynthesis in this region of nuclides, an independent experiment is being planned, based on activation in the quasi-Maxwellian neutron field ($kT \sim 5\,\mathrm{keV}$) of the ${}^{18}$O(p,n) reaction close to threshold. This experiment will enable direct comparison between a quasi-Maxwellian activation and the time-of-flight measurement without the need of extrapolation and hence has the potential to resolve the discrepancy. The ${}^{18}$O(p,n) reaction was originally proposed by Heil et al. [5] for astrophysical MACS determinations and its study was recently revisited [6] for our experiments. With a proton beam of $2581\,\mathrm{keV}$ incident on a ${}^{18}$OTa$_2$O$_5$ target at the PTB-PIAF facility, the outgoing neutron energy distribution was measured by means of time of flight with a thin ${}^{6}$Li detector at angles of $0^\circ - 60^\circ$. The angle-integrated neutron spectrum closely resembles a thermal flux distribution at $kT= 5\,\mathrm{keV}$. The results, under final analysis stages, will be presented.

M.F. and M.P. acknowledge support by the European Union (ChETEC-INFRA, project no. 101008324).

[1] R.N. Sahoo et al., Phys. Rev. C 109, 025808 (2024).
[2] S. Amaducci et al., Phys, Rev. Lett. 132, 122701 (2024).
[3] I. Dillmann et al., AIP Conf. Proc. 819, 123 (2006).
[4] K. Wright, APS Physics Magazine, March 25, 2024.
[5] M. Heil et al., Phys. Rev. C 71, 025803 (2005).
[6] M. Friedman, "Measurement of Thick-Target ${}^{18}$O(p,n)${}^{18}$F Neutron Energy Spectrum, Yield and Angular Distribution at $E_p=2582\,\mathrm{keV}$", ChETEC-INFRA 2nd General Assembly, 20 June 2022, Padova, Italy.

Speaker: Moshe Friedman (The Hebrew University of Jerusalem)

Moshe_Friedman_NPA_XI_140Ce.pptx

Öffentlicher Abendvortrag (Public Evening Lecture, in German)

188 Die Entstehung der chemischen Elemente im Universum

Speaker: Friedel Thielemann (Department of Physics, University of Basel, Klingelbergstrabe 82, CH-4056 Basel, Switzerland)

Dresdenfkt.pdf

Wednesday 18 September

Plenary Session: I: Neutron capture processes (4). & New tools and techniques (3).

Convener: Beatriz Jurado

189 Neutron Sources in Stars

About half of the heavy elements in nature are created at the end of core helium burning in massive stars (weak $s$-process) and during the AGB phase of low-mass stars (main $s$-process). These astrophysical environments have been identified as $s$-process sites because reactions are available that produce neutrons on an appropriate time scale and quantity. The ${}^{13}\mathrm{C}(\alpha,\mathrm{n}){}^{16}\mathrm{O}$ reaction is thought to serve as the primary source for the main $s$-process while the ${}^{22}\mathrm{Ne}(\alpha,\mathrm{n}){}^{25}\mathrm{Mg}$ reaction does so for the weak $s$-process. In addition, reactions such as ${}^{17,18}\mathrm{O}(\alpha,\mathrm{n}){}^{20,21}\mathrm{Ne}$ and ${}^{25,26}\mathrm{Mg}(\alpha,\mathrm{n}){}^{28,29}\mathrm{Si}$ act as secondary sources that counteract neutron poisons. First generation stars may also be a sight for this type of nuecleosyntheis through the ${}^{10,11}\mathrm{B}(\alpha,\mathrm{n}){}^{13,14}\mathrm{N}$ reactions. Yet because of the needed cross sections are at low energies where they are very small, it makes them extremely challenging to measure directly in the laboratory. Compounded with the challenges of neutron detection, the uncertainties of most of these reactions remain some of the largest contributors to stellar model calculations. However, it is a very exciting time because, several new measurements have made rapid progress in reducing these uncertainties. In this talk, I will review the present state of uncertainties in light of these new measurements.

Speaker: Richard deBoer (University of Notre Dame)

deBoer_NPA_2024.pdf

190 2D chemical evolution model of ${}^{26}$Al and ${}^{60}$Fe

$^{26}$Al and $^{60}$Fe are two short-lived radioactive nuclei that can be used as tracers of the star formation. In the next years, COSI, the new $\gamma$-ray instrument by NASA will be launched and will provide us with a new insight of the distribution of these two elements in the Milky Way. In view of these new upcoming measurements, by means of a detailed 2D chemical evolution model I provide a theoretical 2D map of the $^{26}$Al and $^{60}$Fe mass distribution. I test several different combinations of initial parameters such as the present time nova rate and the star formation efficiency to highlight which is the best one to reproduce observational constraints (such as present day star formation, supernova rate and gas mass) together with the $^{26}$Al and $^{60}$Fe observations provided by previous instruments. We are also able to produce a flux map as function of the Galactic longitude that can be compared to those provided in the past years by COMPTEL and INTEGRAL to identify which are the lines of sight were overproduction of these two elements is observed.

Speaker: Arianna Vasini (University of Trieste, Department of Physics)

Presentation_Vasini_#68.pdf

191 Neutron capture and total cross-section measurements on ${}^{94,95,96}$Mo at n$\_$TOF and GELINA

Cross-sections for neutron-induced reactions with molybdenum is relevant in various scientific fields ranging from nuclear astrophysics to nuclear technologies. In addition to its astrophysical role, molybdenum isotopes can be found in fission power plants as fission products and the use of this material is under study for future improved reactors. Molybdenum is found in pre-solar silicon carbide grains and an accurate knowledge of its neutron capture cross section plays a crucial role in constraining stellar nucleosynthesis models, particularly for AGB stars. A deviation in the model predictions of isotopic composition in SiC grains has been observed when using Mo cross-section data from the two main KADoNiS versions.

Nevertheless, experimental data for the neutron capture cross-section found in the literature for Mo isotopes suffer from large uncertainties. This is also reflected in the large uncertainties of the cross-sections recommended in the ENDF/B-VIII.0 library and in the uncertainty of the MACS found in the KADoNiS database, which is of the order of $10\%$ at $30\,\mathrm{keV}$.

In this contribution the first preliminary results of transmission and radiative neutron capture measurements performed at $\mathrm{n\_TOF}$ (CERN, Switzerland) and GELINA (EC-JRC Geel, Belgium) for $^{94,95,96}$Mo will be presented.

Speaker: Riccardo Mucciola (INFN Bari)

NPA_XI_Mo_Mucciola.pdf

192 The new grid of CO5BOLD 3D hydrodynamical red giant model atmospheres and its application to globular cluster abundance estimates

To interpret stellar spectra 1D hydrostatic model atmospheres are most often used as a compromise between accuracy and computational cost. However, such models do not treat convection accurately and rely on approximating it with varying degrees of success. We present a new grid of 3D hydrodynamic CO5BOLD model atmospheres and use it with 3D non-equilibrium radiative transfer code MULTI3D to investigate whether accurate treatment of both hydrodynamics and radiative transfer can explain anomalies in abundance estimates in red giants of globular clusters for Mg and Al spectral lines, which were obtained with simpler 1D hydrostatic model atmospheres assuming local thermodynamic equilibrium.

Speaker: Jonas Klevas (Max Planck Institute for Astronomy, Heidelberg, Germany; Institute of Theoretical Physics and Astronomy (ITPA), Vilnius, Lithuania)

2024-NPI-Dresden-JK.pdf

193 Indirect experimental approaches to charged particle reactions in astrophysics

Due to the Coulomb barrier or the low-intensities of radioactive ion beams (or both!), indirect approaches to determining thermonuclear reaction rates are vital. There are many different tools, ranging from improving spectroscopy of nuclei to constrain resonance properties using charged-particle or $\gamma$-ray spectroscopy to identify resonance states and determine their spins and parities, to using transfer reactions to access information about partial widths.

In this talk, I will introduce recent developments in indirect methods for determining charged particle-induced reactions with a focus on different techniques which can be used to try to answer specific questions about importanat astrophysical reaction rates.

Speaker: Philip Adsley (Texas A&M University)

PAdsley_NPA_Sep2024.pdf

194 ELI Silicon Strip Array (ELISSA) at ELI-NP

ELISSA is a 4π silicon strip detector array implemented at the ELI-NP facility for measurements of photodissociation reactions using high-brilliance, quasi-monoenergetic gamma beams. The array consists of three rings of 35 single-sided X3 detectors and two end-caps made up of eight double-sided QQQ3 detectors. However, multiple configurations are possible with the YY1, MMM, and QQQ3 detectors as end-caps detectors. Recently, new direct measurements of the ${}^{19}\mathrm{F}(p,\alpha){}^{16}\mathrm{O}$, ${}^{7}\mathrm{Li}(p,\alpha){}^{4}\mathrm{He}$, and ${}^{6}\mathrm{Li}(p, \alpha){}^{3}\mathrm{He}$ reactions at astrophysical energies were successfully carried out with the scaled-down version of the ELISSA detector array at the IFIN-HH 3\,MV Tandem. The mini-ELISSA chamber and $\mathrm{CH}_2$ targets were used for these measurements.

Presently, ELISSA needs to upgrade to a larger chamber as mini-ELISSA has limitations in using available detector configurations. In this regard, the Monte Carlo simulation has been carried out with multiple configurations using the YY1, MMM, QQQ3, and X3 detectors both for gamma beam and ion beams. For example, a simulation of ${}^{7}\mathrm{Li}(\gamma,t){}^{4}\mathrm{He}$ reaction with the MMM and YY1 Silicon Detectors was completed and the ${}^{7}\mathrm{Li}(\gamma,t){}^{4}\mathrm{He}$ experiment was also successfully carried out at HIgS using the YY1 detectors.

In this talk, detailed activity using the ELISSA array at ELI-NP will be presented.

Speaker: Haridas Pai (Extreme Light Infrastructure-Nuclear Physics (ELI-NP), Horia Hulubei National Institute for R&D in Physics andNuclear Engineering (IFIN-HH))

1035_Pai.pptx

10:50 Coffee Break

Plenary Session: J: New tools and techniques (4).

Convener: Almudena Arcones (TU Darmstadt)

195 Surrogate reactions in inverse kinematics at heavy-ion storage rings

Obtaining reliable cross sections for neutron-induced reactions on unstable nuclei nuclei is crucial to our understanding of the stellar nucleosynthesis of heavy elements. However, the measurement of these cross sections is very complicated, or even impossible, due to the radioactivity of the targets involved. Our aim is to circumvent this problem by using the surrogate-reaction method in inverse kinematics at heavy-ion storage rings, which offer unique and largely unexplored possibilities for the study of nuclear reactions.

In this talk, I will present the technical developments and the methodology, which we are developing to perform high-precision surrogate-reaction experiments at the Experimental Storage Ring (ESR) of the GSI/FAIR facility. In particular, I will present the results of the first experiments, which we recently conducted at the ESR, and briefly describe the perspectives for future measurements.

Speaker: Beatriz Jurado Apruzzese (LP2I, Bordeaux, France)

196 Detection of time-resolved influxes of supernova-produced $^{60}$Fe and r-process $^{244}$Pu onto Earth over the last 10$\,$Myr

Live radionuclides that were synthesised and ejected by stellar explosions, dispersed in the interstellar medium and subsequently deposited on Earth provide key insights about the astrophysical history of the solar neighbourhood and heavy element nucleosynthesis. The influx of supernova-produced $^{60}$Fe (t$_{1/2}$$\,$=$\,$2.6$\,$Myr) about 2.5$\,$Myr ago was reported several times within the last two decades. The longer-lived pure r-process nuclide $^{244}$Pu (t$_{1/2}$$\,$=$\,$81$\,$Myr) was only recently detected owing to the advancement of the single-atom counting technique AMS (accelerator mass spectrometry). The time-structure of both radionuclide influxes could provide direct experimental evidence on interstellar medium dynamics, r-process nucleosynthesis sites and the last r-process event in the solar neighbourhood.

In this contribution, I will present time-resolved profiles of both $^{60}$Fe and $^{244}$Pu in the large ferromanganese crust VA13/237KD covering the last 10$\,$Myr. The measured profile of $^{60}$Fe clearly shows two distinct influxes confirming and refining previous results. The updated timing of the $^{60}$Fe arrival can be used to further constrain the location of the progenitor star. A clear detection of r-process $^{244}$Pu will be reported. The time-profile of $^{244}$Pu will be interpreted with respect to the established $^{60}$Fe influxes and an outlook on further r-process radionuclides and geological archives will be given.

Speaker: Dr Dominik Koll (The Australian National University & TU Dresden & Helmholtz-Zentrum Dresden-Rossendorf)

197 BETAFLOWNET: A Practical Nuclear Network Geared Towards Coupling with Hydrodynamics Simulations

Accounting for out-of-NSE (nuclear statistical equilibrium) r-process nucleosynthesis is one of the most sought-after goals in the (numerical) modelling of binary neutron star (BNS) mergers. While post-processing analysis via full nuclear networks is a reliable technique, the computational and storage costs prevent such calculations to be directly coupled to hydrodynamics codes, thus neglecting the dynamical influence of the r-process heating. We present here a novel framework, akin to a reduced network, based on top of the "beta-flow" approximation, that drastically reduces the computational and storage requirements w.r.t. a full network while returning accurate predictions for both isotope abundances and heating rate. This technique features: 1) far less degrees of freedom than a full network ($\sim 500$ vs. $\sim 7500$); 2) explicit split between dominant/subdominant and fast/slow reactions; 3) ability to accurately track the time evolution of abundances and heating rate. We summarize its base assumptions and derivation, practical implementation issues, and its application to parametrized BNS ejecta along with a detailed comparison w.r.t. to full networks such as SkyNet and WinNet. Finally, we show the first results of BNS merger simulations with inline nucleosynthesis performed with this model.

Speaker: Federico Maria Guercilena (Università di Trento)

talk_Guercilena.pdf

198 Development of the COREA detector system for the measurement of the $^{12}$C$(\alpha,\gamma)^{16}$O reactions

We have developed a compact detector system that utilizes an active-target TPC (Time Projection Chamber) to measure the $^{12}$C$(\alpha,\gamma)^{16}$O reaction. This system includes a 3-T superconducting magnet, a low-pressure He-gas TPC, and a LaBr$_3$(Ce) detector array. The proposed experiment, called COREA (Carbon Oxygen Reaction Experiment with Active-target TPC) experiment, will take place at the BIBA heavy-ion accelerator facility in Korea. The TPC has triple GEM (Gas Electron Multiplier) and gating GEM layers. It has a readout plane that covers an area of $10\times 10$ cm$^2$ and contains 1000 $3\times 3$ mm$^2$ square pads. The TPC uses a gate operation and an opaque part of the gating GEM layer to block the beam-associated signal amplification. The gamma-ray detector array comprises 16 cylindrical LaBr$_3$(Ce) detectors, each with a 50 mm diameter and 75 mm long crystal. We have tested the TPC and LaBr$_3$(Ce) array using radioactive sources and ion beams from the KIST tandem accelerator facility. This presentation will give an update on the current status of the COREA experiment and showcase the performance of the unique COREA detector system.

Speaker: Jung Keun Ahn (Korea University)

NPA-XI_Sep18Wed_JungKeunAhn.pdf

199 Nuclear Astrophysics Masterclasses - Fingerprints of the Stars

Masterclasses are one-day outreach events for high school students, introducing them to topics of current research. Within the framework of the EU project ChETEC-INFRA, Masterclasses on Nuclear Astrophysics have been developed. This interdisciplinary field of science provides a new didactic perspective on nuclear and astrophysical processes by addressing the link between these two subjects. The Nuclear Astrophysics Masterclasses pick up this didactic potential. They include the spectroscopic analysis of metal poor stars with WebSME. Furthermore, the processes behind the formation of the first chemical elements are reconstructed with the help of various gamification elements as well as hands-on activities. Emphasis is placed on current research topics in nuclear astrophysics, in particular the primordial lithium problem. The talk will present the teaching materials, the didactic concept, the experiences made so far in the implementation as well as possibilities of utilizing the Masterclasses for PhD outreach training.

Speaker: Hannes Nitsche (Technische Universität Dresden)

Nitsche_NuclearAstrophysicsMasterclasses_NPAXI.pptx

12:55 Lunch Break

13:55 Transfer to City Center (self-organized)

Social Event: Guided tour of Dresden City Center

Meeting point 14:45 on the steps of the Catholic Cathedral (Katholische Hofkirche), Tram 3 stop "Theaterplatz"

Social Event: Reception and conference dinner - NEW LOCATION Feldschlösschen Stammhaus

Meeting point 14:45 on the steps of the Catholic Cathedral (Katholische Hofkirche), Tram 3 stop "Theaterplatz"

Thursday 19 September

Plenary Session: K: Cosmochemistry and Galactic Chemical Evolution (2). & Gravitational waves (1).

Convener: Artemis Spyrou (Michigan State University)

200 Chemically pristine stars in the Milky Way

The lowest metallicity stars that still exist today represent a window into the early Universe. Studying these stars gives us a local avenue to guide our understanding of star formation and supernova feedback in the early Universe, the early build-up of galaxies like our Milky Way, and the epoch of reionization.

In this talk I will review how we have become very efficient at finding these stars and what they have started to tell us about the early assembly phase of the Milky Way as well as the nature of some of its most intriguing stellar substructures. Moreover, I will highlight the bright future for this type of study in synergy with the upcoming massively multi-plexed stellar surveys such as WEAVE and 4MOST.

Speaker: Else Starkenburg (Kapteyn Astronomical Institute, University of Groningen)

201 Probing high density physics in the gravitational wave astronomy era

The recent multimessenger detections of signals from neutron star binaries has opened a new era also for the study of high density physics. With interior densities that can exceed those of an atomic nucleus, and low temperatures (at least in mature systems) compared to the Fermi temperatures of the constituents, neutron stars allow to probe very different and complementary regimes of the QCD phase diagram, compared to terrestrial experiments. In this talk I will discuss some of the recent observations, and show how gravitational wave detections, especially if coupled with electromagnetic observations, can allow to make progress on constraining the equation of state of dense matter. In particular, I will not only discuss compact binary coalescences (that have already been observed in gravitational waves), but also long lived quasi-monochromatic signals, i.e. `continuous' waves, that are still currently unobserved, but may allow for new and significant constraints.

Speaker: Bryn Haskell (Nicolaus Copernicus Astronomical Center, PAS)

HaskellDresden24.pdf

202 Chemical evolution of neutron-capture elements across the Milky Way

The majority of elements beyond the Fe peak are produced by neutron capture processes which can be rapid (r-process) or slow (s-process) with respect to the $\beta$-decay in nuclei. Understanding which are the astrophysical formation sites of these two processes has become one of the major challenges in chemical evolution. In particular, the r-process sites are still under debate, with possible main producers candidates being peculiar supernovae (magneto-rotational supernovae, MR-SNe) or merging of compact objects (neutron stars or neutron star-black hole).

In this talk, I will first present the main steps done in chemical evolution simulations to understand the origin of neutron capture elements and then I will show results from our latest work. We studied both the abundance patterns and the radial gradients of five s-process elements (Y, Zr, Ba, La, Ce) and four mixed/r-process elements (Eu, Mo, Nd, Pr) in the Galactic thin disc using a detailed two-infall chemical evolution model with state-of-the-art nucleosynthesis prescriptions. Predictions of our model are compared with data from the sixth data release of the Gaia-ESO survey, which consists of 62 open clusters located at different Galactocentric distances and with ages ranging from $0.1$ to $7\,\mathrm{Gyr}$, and 1300 disc field stars.

Speaker: Marta Molero (TU Darmstadt)

MartaMolero_NPA-XI_2024.pdf

203 The contribution of massive stars to the chemical evolution of the Galaxy

Massive stars play a crucial role in shaping the chemical composition of galaxies, enriching the interstellar medium with both light and heavy elements previously synthetized in the star through nuclear reactions. Recent advancements in stellar modelling have highlighted the beneficial effects of rotation in massive stars, enhancing the nucleosynthesis of certain elements, especially at low metallicities where stars are more compact and expected to rotate faster. Thanks to the large amount of recent and forthcoming observations, it is possible to improve Galactic chemical evolution models to reproduce the evolutionary history of the isotopic abundances measured in stars, therefore constraining the sites and production mechanisms responsible for the synthesis of the different elements.

In this talk, I will present results coming from chemical evolution models that include the nucleosynthesis from rotating massive stars, employed to explain and reproduce the evolutionary patterns of some key light and heavy elements, deriving some significative constraints on the structure and nucleosynthesis of massive stars.

Speaker: Federico Rizzuti (Università degli studi di Trieste)

Rizzuti NPA-XI.pdf

204 Nuclear Astrophysics meets Asteroseismology

Massive stars play an important role in the synthesis of new elements in the Universe. To understand the nucleosynthetic wind-yields of such stars, there are three key-ingredients; the nuclear reaction-rates, internal mixing processes, and the stellar winds. We focus on the effects of interior mixing processes. Up to now, the calculations of stellar yields have relied on stellar evolution models that are uncalibrated in terms of chemical mixing in the stellar interior. We take the recent observationally driven advances in asteroseismic analysis of the interior structure and the proposed mixing profiles based on them into account. This way, our models connect theoretical yield calculations and asteroseismically calibrated mixing profiles. This is a vital step to improve our understanding of the evolution of stars with initial masses within the supernova-range and their role in enriching the galaxy. Due to the strong dependence between the interior structure of a supernova-progenitor and its final fate, changes in the interior mixing of these stars affects the nucleosynthetic yields, and might also affect which stars end as supernovae. Therefore, a proper understanding of the impact of this calibrated mixing on stellar evolution is especially valuable for the community working on nucleosynthesis and galactic chemical evolution.

Speaker: Hannah Brinkman (Institute of Astronomy, KU Leuven)

NPAXI-HEBrinkman.pdf

205 A recipe for using binary stellar yields in galactic chemical evolution calculations

Galactic chemical evolution calculations provide invaluable feedback between abundance surveys and stellar and nuclear physics models. Until recently, only yields from single stars have been available, so chemical evolution codes do not have the capability to build a mixed population of binary and single stars. This is a serious limitation, as most stars – particularly the most massive – form in binaries, and follow different evolution pathways that affect their yields. In this talk, we present our framework for calculating ‘effective binary stellar yields’ which account for the evolution of both the primary and the secondary stars. These effective binary yields can be included in existing chemical evolution codes as if they were single stellar yields. We provide a checklist of the outputs from binary stellar models that are required to fully exploit binary stellar yield calculations of stable and radioactive isotopes. We also present our results on how assumptions around the mass transfer efficiency and birth distributions – including the binary mass fraction – affect the binary stellar yields and lifetimes.

Speaker: Alex Kemp (KU Leuven)

binary_stellar_yields.pdf

10:50 Coffee Break

Plenary Session: L: Neutron stars (2). & Explosive processes (2).

Convener: Jenny Feige

206 Atomic cascade computations for astrophysics

Atomic cascades are ubiquitous in nature and have therefore been explored within many different scenarios, from atoic precision measurements to the modeling of astrophysical spectra, and up to the radiation transport in neutron-star mergers. We here introduce and discuss a classification of atomic cascades and demonstrate how they can be modeled efficiently [1,2].

In practice, however, most atomic and ionic cascades are rather complex and have hampered in the past a detailed account owing to the large (or even huge) number of decay paths. To overcome these difficulties in modeling the ionic ionization, capture and decay processes, we make use of JAC, the Jena Atomic Calculator [3], that help analyze a wide range of atomic shell structures. Apart from first classifying the underlying processes, we here explain how cascade computations and simulations should be distinguished in order to keep the modeling of cascades feasible.

[1] Fritzsche S, Palmeri P and Schippers S 2021 Symmetry 13 520
[2] Fritzsche S et al., submitted to EPJD (2024).
[3] Fritzsche S 2019 Comp. Phys. Commun. 240 1; https://github.com/OpenJAC/JAC.jl

Speaker: Stephan Fritzsche (HI-Jena)

b24.dresden-nuclear-astro-sep.pdf

207 Combining nuclear physics and multi-messenger observations

Our knowledge about dense matter explored in the cores of neutron stars remains limited. Fortunately, the detections of gravitational waves emitted from the merger of neutron stars and the corresponding electromagnetic signals provide a new way of studying supranuclear-dense material. Making use of the strength of multi-messenger astronomy, one can combine the information obtained from gravitational-wave observations, the electromagnetic counterparts of merging neutron stars with the information provided by NICER, radio pulsar observations, and heavy-ion collision experiments to derive new constraints on the neutron-star equation. We outline how the combination of current theoretical knowledge, astrophysical observatories, and experimental facilities helps us to improve our knowledge about the supranuclear-dense equation of state and what we can expect from the next generation of experiments.

Speaker: Tim Dietrich (University of Potsdam)

Dietrich_Tim.pptx

208 Production of $p$-nuclei from $r$-process seeds: the $\nu r$-process

We present a new nucleosynthesis process that may take place on neutron-rich ejecta experiencing an intensive neutrino flux. The nucleosynthesis proceeds similarly to the standard $r$-process, a sequence of neutron-captures and beta-decays, however with charged-current neutrino absorption reactions on nuclei operating much faster than beta-decays. Once neutron capture reactions freeze-out the produced $r$-process neutron-rich nuclei undergo a fast conversion of neutrons into protons and are pushed even beyond the $\beta$-stability line producing the neutron-deficient $p$-nuclei. This scenario, which we denote as the $\nu r$-process, provides an alternative channel for the production of $p$-nuclei and the short-lived nucleus $^{92}$Nb. We discuss the necessary conditions posed on the astrophysical site for the $\nu r$-process to be realized in nature. While these conditions are not fulfilled by current neutrino-hydrodynamic models of $r$-process sites, future models, including more complex physics and a larger variety of outflow conditions, may achieve the necessary conditions in some regions of the ejecta.

[1] Z. Xiong, G. Martínez-Pinedo, O. Just, A. Sieverding, arXiv:2305.11050 (accepted by PRL)

Speaker: Zewei Xiong (GSI Helmholtzzentrum für Schwerionenforschung)

NPA_XI_Xiong.pdf

209 Rare nuclei production in core-collapse supernovae: the γ-process nucleosynthesis

Neutron-capture processes made most of the abundances of heavy elements in the Solar System, however they cannot produce a number of rare neutron deficient stable isotopes (p-nuclei) lying on the left side of the valley of stability. The $\gamma$-process is recognised and generally accepted as a feasible process for the synthesis of p-nuclei in core-collapse supernovae. However this scenario still leaves some puzzling discrepancies between theory and observations.

My aim is to explore in more detail the p-nuclei production from massive stars in different sets of models and using the latest nuclear reaction rates. Here I will show some of the result of my analysis, by identifying several efficient $\gamma$-process sites and focusing on supernova progenitors that experience a C-O shell merger just before the collapse of the Fe core. I will also discuss how the $\gamma$-process depends on the supernova explosion energy and on the prescription used to calculate the core-collapse supernova.

Speaker: Lorenzo Roberti (Konkoly Observatory, CSFK HUN-REN)

NPAXI_Roberti.pdf

210 Collective neutrino oscillations and the heavy-element nucleosynthesis in supernova

In high energy astrophysical processes involving compact objects, such as core-collapse supernovae or binary neutron star mergers, neutrinos are likely to play an important role in the synthesis of nuclides. Neutrinos in these environments can experience collective flavor oscillations driven by neutrino-neutrino coherent forward scattering. Recently, there has been interest in exploring potential beyond-the-mean-field effects in the collective oscillations of neutrinos. Here, we seek to explore possible implications of these effects for the heavy-element nucleosynthesis yields in supernova environments with different astrophysical conditions and neutrino inputs. We find that collective oscillations can impact the operation of the νp-process and r-process nucleosynthesis in supernovae. The potential impact is particularly strong in high-entropy, proton-rich conditions, where we find that neutrino interactions can nudge an initial $\nu \mathrm{p}$ process neutron rich, resulting in a unique combination of proton-rich low-mass nuclei as well as neutron-rich high-mass nuclei. We describe this neutrino-induced neutron capture process as the "$\nu \mathrm{i}$ process". In addition, nontrivial quantum correlations among neutrinos, if present, could lead to distinctly different nucleosynthesis results compared to the corresponding mean-field treatments, by virtue of modifying the evolution of the relevant one-body observables.

Speaker: Xilu Wang (Institute of High Energy Physics, Chinese Academy of Sciences)

211 Study of the alpha-nucleus optical potential in the mass range relevant to the gamma-process nucleosynthesis

Experimental data collected in the last two decades give a clear indication that the low-energy alpha-nucleus optical potential ($\alpha$-OMP) is a crucial and not sufficiently known nuclear physics parameter in the modeling of the $\gamma$-process of heavy element nucleosynthesis. A new $\alpha$-OMP called Atomki-V2 has been developed for low energy nuclear astrophysics purposes [1]. This potential provides a reproduction of most of the available experimental reaction cross sections better than the other available global $\alpha$-OMPs. In this presentation, after giving a brief description of the experiments, the performance of this potential will be examined further in the case of two recent ($\alpha$,n) cross section measurements on $^{144}$Sm [2] and on several Te isotopes [3].

[1] P. Mohr et al. At. Data Nucl. Data Tables 142, 101453 (2021)
[2] Gy. Gyürky et al., Phys. Rev. C 107, 025803 (2023)
[3] Zs. Mátyus et al., Phys. Rev. C submitted

Speaker: György Gyürky (Institute of Nuclear Research (ATOMKI))

gyurky_NPAXI_talk.pptx

13:10 Lunch Break

Plenary Session: M: Neutron star (3). & New tools and techniques (5).

Convener: François de Oliveira

212 Neutron star mergers and their nucleosynthesis

The discovery of a slowly inspiralling binary system of two neutron stars by Hulse and Taylor in 1974 made clear that the final fate of such a system would be a very violent collision between the compact stars and that -at the very least- "something interesting" would happen. Based on indirect and mostly theoretical arguments, such collisions where connected to gamma-ray bursts and also to the potential formation "rapid neutron capture", or r-process, elements. The firm experimental confirmation of these ideas, however, had to wait until August 2017 when the gravitational waves from a neutron star merger inspiral flooded the LIGO detectors for about one minute. Subsequently, telescopes all around the world detected a firework of electromagnetic emission all across the spectrum which demonstrated that some r-process was produced. In this talk I will give an overview over our current understanding of the heavy element formation in neutron star mergers.

Speaker: Prof. Stephan Rosswog (University Hamburg, Germany & Oskar Klein Centre Stockholm, Sweden)

213 Recent Studies of Astrophysical Reactions at the TRIUMF-ISAC Facility

Understanding the origin of the elements, particularly elements heavier than iron, is consistently identified as a major research challenge in nuclear physics. Meeting this challenge demands new approaches to overcome extreme technical difficulties posed by reaction studies, especially those that necessitate the use radioactive ion beams. In this talk, I will present the recent progress of nuclear astrophysics research with accelerated beams at the TRIUMF-ISAC facility, followed by a discussion of ideas to expand this program into the future. Discussed topics will include the astrophysical p-process, weak r-process and stellar burning in ancient stars, focusing on studies performed using the DRAGON experiment and the recently commissioned joint EMMA-TIGRESS facility.

Speaker: Dr Matthew Williams (University of Surrey)

214 Nuclear physics inputs for neutron stars and nucleosynthesis simulations

Nuclear physics plays an important role for many astrophysics applications. Nucleosynthesis simulations of heavy elements, for example, require nuclear inputs across the whole nuclear chart, far beyond the region where experimental data is available. Likewise, the description of the extremely dense neutron-rich matter in neutron stars (NS) is a challenge for nuclear physics and astrophysics.
We will present the new family of global nuclear structure models which aims to provide accurate nuclear physics inputs to astrophysical applications. The latest Brussels-Skyrme-on-a-Grid model (BSkG3) [2] greatly improves the infinite nuclear matter properties (INM) as compared to earlier BSkG parametrizations. Compared to its predecessors, BSkG3 offers a more realistic description of matter at the extreme densities relevant to NS and is consistent with observations of heavy pulsars, in contrast to most Skyrme parameterizations. Reconciling the complexity of NS with those of atomic nuclei establishes BSkG3 as a tool of choice for applications in nuclear astrophysics.
We will also present our efforts to create a new model which aims to improve the nuclear inputs to NS mergers simulations, while keeping an accurate description of nuclear structure properties.
[1] G. Grams, et al, EPJA 59, 270 (2023).

Speaker: Guilherme Grams (Institut d’Astronomie et d’Astrophysique (IAA), Université Libre de Bruxelles, Belgium.)

GGrams-NPA-sept24.pdf

215 Elements formation in radiation-hydrodynamics simulations of kilonovae

I'll present the results from a self-consistent 2-dimensional (ray-by-ray) radiation-hydrodynamic simulation of BNSM ejecta with an online nuclear network (NN) up to the days timescale. An initial numerical-relativity ejecta profile composed of the dynamical component, spiral-wave and disk winds is evolved including detailed $r$-process reactions and nuclear heating effects. A simple model for the jet energy deposition is also included.
I'll discuss how the commonly assumed approach of relating the final nucleosynthesis yields to the initial thermodynamic profile of the ejecta can lead to inaccurate predictions and what are the main deviations we find compared with results obtained by using NN in post-processing. I'll also analyze the effects of the polar jet on nucleosynthesis patterns and kilonova light curves

Speaker: Fabio Magistrelli (FSU Jena, TPI)

240919_NPAXI_Magistrelli.pdf

15:30 Coffee Break

Plenary Session: N: Neutron stars (4). & Explosive processes (3).

Convener: Zsolt Podolyák (University of Surrey)

216 Interferometric gravitational wave detection - a (quantum) metrological challenge

Since the first direct detection of gravitational waves in 2015, we have gained an entirely new observation window to the universe. The sensitivity of these interferometers is so incredible that the quantum effects of the laser light have become limiting. Ultra-precisely stabilised lasers do not suffice; non-classical light is already routinely employed in the current generation of gravitational wave detectors (e.g. aLIGO & AdVirgo). Other noise sources, such as seismic and thermal noise, pose further challenges for next-generation detectors.

To achieve ever-higher detection rates for meaningful gravitational wave astronomy, ever-greater detection sensitivity is required. I will briefly introduce the principle of interferometric gravitational wave detection (for any students present) and highlight some of the advanced technologies implemented. The European Project „Einstein Telescope“, a third-generation observatory, will also be featured. I will conclude my talk by showing some further possibilities related to this, as well as options for quantum noise reduction in laser interferometry.

Speaker: Michèle Heurs (Leibniz University Hannover; German Center for Astrophysics (DZA))

NPA_XI_Heurs_QE_GWD_Dresden_Sept2024.pdf

217 Neutron-star merger simulations including all phases of matter ejection

Neutron star mergers lead to the ejection of multiple outflow components. Many existing neutron-star merger models cover only the first tens of milliseconds after the merger and can therefore only describe the early, dynamical ejecta. However, further matter ejection can take place during several seconds of evolution of the merger remnant. In this talk I will present our recent study [1] investigating long-term evolution models that consistently followed the dynamical ejecta together with the ejecta driven by the hyper-massive neutron-star as well as the subsequent black-hole torus system. Apart from the hydrodynamics properties I will discuss the nucleosynthesis yields and approximate kilonova light curves of these models.

[1] "End-to-end Kilonova Models of Neutron Star Mergers with Delayed Black Hole Formation"; O. Just, V. Vijayan, Z. Xiong, S. Goriely, T. Soultanis, A. Bauswein, J. Guilet, H.-Th. Janka, G. Martínez-Pinedo, The Astrophysical Journal Letters, 951, L12, 2023.

Speaker: Oliver Just (GSI Helmholtzzentrum für Schwerionenforschung)

Just_talk_NPA.pdf

218 Multi-dimensional kilonova radiative transfer simulations

The detection of the kilonova AT2017gfo has provided us with a wealth of observations. However, to interpret these observations to obtain information about the underlying merger ejecta, including r-process nucleosynthesis, we are reliant on kilonova modelling. The majority of binary neutron star ejecta models considered when simulating kilonovae have been in 1D, or even idealised toy models, which have neglected the complexities related to hydrodynamics modelling. I will show that 3D kilonova radiative transfer simulations are critical, due to the asymmetric nature of these events, and will present results on a 3D simulation from hydrodynamical merger ejecta using line-by-line opacities from millions of r-process transitions. I will also highlight the necessity of accurate atomic data of r-process elements, for which experimentally obtained data is highly incomplete.

Speaker: Christine Collins (GSI Helmholtz Centre for Heavy Ion Research)

219 Studying Explosive Binary Systems with Nuclear Spectroscopy

Type-I X-ray bursts are interpreted as thermonuclear runaways in the atmospheres of accreting neutron stars in close binary systems. These astronomical events exhibit brief, recurrent bursts of intense X-ray emission and represent some of the most frequent and violent stellar explosions to occur in our Galaxy. Recently, space-borne satellites such as the Rossi X-ray Timing Explorer (RXTE) and the Chandra X-ray telescope have produced a wealth of observational data on Type-I X-ray bursts, marking a new era of X-ray astronomy. However, in spite of these remarkable developments, many key questions about the exact nature of X-ray bursts remain, particularly in relation to the exact shape and structure of the observed light curves. As such, in order to fully exploit the remarkable achievements of X-ray astronomy, similar advances in our understanding of the underlying nuclear physics processes governing nucleosynthesis and energy generation are required.

X-ray bursts are powered by a sequence of nuclear reactions known as the rp (rapid proton) process - a series of $(\mathrm{p},\gamma)$ captures and subsequent $\beta^+$ decays, synthesizing elements up to the Sn-Te mass region. This is a complex reaction network involving hundreds of nuclei from stable isotopes to the proton dripline. With recent advancements in computational power, it has become possible to construct detailed models of the rp-process nucleosynthesis and study the influence of nuclear reaction rate uncertainties. In particular, it has been shown that reactions around "waiting-point" nuclei have a significant effect on the resulting light curves. Specifically, the ${}^{48}\mathrm{Cr}(\mathrm{p},\gamma){}^{49}\mathrm{Mn}$ and ${}^{59}\mathrm{Cu}(\mathrm{p},\gamma){}^{60}\mathrm{Zn}$ reactions have been highlighted as being especially important. In this talk, spectroscopic studies of the nuclei ${}^{49}\mathrm{Mn}$ and ${}^{60}\mathrm{Zn}$ will be presented with a key emphasis on proton-unbound states that determine the rates of the astrophysical ${}^{48}\mathrm{Cr}(\mathrm{p},\gamma){}^{49}\mathrm{Mn}$ and ${}^{59}\mathrm{Cu}(\mathrm{p},\gamma){}^{60}\mathrm{Zn}$ reactions, respectively.

Speaker: Gavin Lotay (University of Surrey)

220 Experimental study of the $^{15}$O($\alpha$,$\gamma$)$^{19}$Ne reaction for understanding type I X-ray bursts

The $^{15}$O($\alpha$,$\gamma$)$^{19}$Ne reaction is a key breakout route from the hot CNO cycle in explosive environments such as type I X-ray bursts. Determining an accurate cross section for the relevant resonant states is critical for a better understanding of the X-ray burst energy production and light-curves, and of the subsequent nucleosynthesis through the $\alpha$p- and rp-processes.

The relevant $^{19}$Ne states for temperatures up to 1 GK were populated using an indirect $^{15}$O($^{7}$Li,t)$^{19}$Ne alpha transfer reaction measurement in inverse kinematics. The experiment used an intense radioactive $^{15}$O beam produced by SPIRAL1 at GANIL and the state-of-the art detection system VAMOS + MUGAST + AGATA, for the detection of the heavy residues, the light charged particles and the de-exciting $\gamma$-rays, respectively. This allowed to reach an unprecedented selectivity for detecting triple coincidences of all final state particles in this reaction.

In this presentation, we will outline the experimental set-up and analysis, providing results for the strongest populated resonances in $^{19}$Ne. In particular, our result with reduced uncertainty for the alpha width of the critical 4.033 MeV excited state will be presented. New astrophysical $^{15}$O($\alpha$,$\gamma$)$^{19}$Ne reaction rates will be presented and the impact on X-ray burst light-curves will be discussed.

Speaker: Nicolas de Séréville (IJCLab / IN2P3)

npa11_deSereville.pdf

221 The ${}^{16}$O(p,$\alpha$)${}^{13}$N reaction in type 1a supernovae

The ${}^{16}$O(p,$\alpha$)${}^{13}$N reaction plays a key role in controlling the Ca/Si and Ca/S ratios synthesized during $\alpha$-rich oxygen burning in Type Ia supernovae (SNIa). This reaction feeds the $\alpha$-rich burning branch by converting ${}^{16}$O into ${}^{12}$C via the chain of ${}^{16}$O(p,$\alpha$)${}^{13}$N($\gamma$,p)${}^{12}$C. Moreover, the ${}^{16}$O(p,$\alpha$)${}^{13}$N rate is highly sensitive to the progenitor white dwarf metallicity. However, current models cannot reproduce all observations using standard reaction rate libraries. Moreover, substantial uncertainties (factors $>2$) exist in available ${}^{16}$O(p,$\alpha$)${}^{13}$N rates, presenting challenges for reliably modelling Type Ia supernova nucleosynthesis.

Therefore, a new direct experimental measurements of the ${}^{16}$O(p,$\alpha$)${}^{13}$N reaction cross section, at center-of-mass energies $E_\mathrm{cm} = 6.9-5.6\,\mathrm{MeV}$, using the MUSIC active-target detector at the ATLAS facility at Argonne National Laboratory was performed. The measured cross sections are used to compute the ${}^{16}$O(p,$\alpha$)${}^{13}$N reaction rate at the relevant temperatures for SNIa models. The results from this work will be presented and the implications for SN1a nucleosynthesis discussed.

Speaker: Alison Laird (University of York)

NPAXI_LAIRD_16Opa13N.pdf

Friday 20 September

Plenary Session: O: Hydrostatic stellar burning (2).

Convener: Alba Formicola

222 Unraveling the mysteries of Carbon-Enriched Metal-Poor (CEMP) stars

In this presentation, the carbon-enriched metal-poor (CEMP) stars will be briefly reviewed. Recent progress in determining the stellar parameters, on the challenges to get benchmark stars within this category, as well as on nucleosynthetic processes that shape the composition of CEMP stars, will be reviewed. CEMP stars exhibit a rich diversity, with at least four distinct types identified. The most prevalent are the CEMP-s stars, characterized by an enrichment of s-process elements. We also encounter CEMP-r stars, CEMP-rs, and CEMP-no stars. The evidence for binarity of some of these classes will be summarized. The attribution of the CEMP-rs chemical peculiarities to the i-process will be discussed. Lastly, we will explore how isotopic ratio diagnostics aid in unraveling the nucleosynthesis process responsible for the chemical peculiarities of CEMP stars, with a presentation of recent findings in this area.

Speaker: Prof. Sophie Van Eck (Université Libre de Bruxelles)

Van_Eck_Dresde_NPA_XI.pdf

223 Recent results for the ${}^{12,13}$C(p,$\gamma$)${}^{13,14}$N reaction cross section in a wide energy range at LUNA and at Felsenkeller laboratory

The ${}^{12,13}\mathrm{C}(\mathrm{p},\gamma){}^{13,14}\mathrm{N}$ are the first reactions of the CNO cycle, active in both hydrostatic and explosive hydrogen burning. They contributes to the ${}^{12}\mathrm{C}$/${}^{13}\mathrm{C}$ isotopic ratio, observed in stellar atmosphere in meteoritic grains and in the interstellar medium. The ${}^{12}\mathrm{C}$/${}^{13}\mathrm{C}$ is a useful tool to study the mixing episodes and nucleosynthesis in Red Giant Branch (RGB) and Asymptotic Giant Branch (AGB) stars. A byproduct of the mixing events and nucleosynthesis taking place in Thermally pulsing AGB stars is the formation of the so called ${}^{13}\mathrm{C}$-pocket, which provides the neutron for s-process nucleosynthesis via the ${}^{13}\mathrm{C}(\alpha,\mathrm{n}){}^{16}\mathrm{O}$ reaction. Moreover the ${}^{12}\mathrm{C}(\mathrm{p},\gamma){}^{13}\mathrm{N}$ reaction is one of the main source of Solar CNO neutrinos, via the ${}^{13}\mathrm{N}$ decay.

Despite their important role in our understanding of stellar nucleosynthesis, up to recent years the ${}^{12,13}\mathrm{C}(\mathrm{p},\gamma){}^{13,14}\mathrm{N}$ reaction rates were poorly constrained by the few data available which are also affected by high uncertainty, with dramatic impact on our predictions for the the ${}^{12}\mathrm{C}$/${}^{13}\mathrm{C}$ isotopic ratio. In recent years, however, these two reactions have been the focus of renewed interest and of many experimental efforts. In the talk I will describe the complementary measurements recently performed at LUNA and at Felsenkeller underground laboratories in a wide energy region. In addition I will present results and I will compare them with previous literature and more recent data.

Speaker: Denise Piatti (University and INFN of Padova)

LUNA_Piatti_200924.pdf

224 Coincidence measurements of fusion reactions involving carbon and oxygen with the high-precision STELlar LAboratory (STELLA)

Fusion reactions involving carbon and oxygen are crucial for the understanding of massive stars and of the nucleosynthesis. Besides $^{12}$C+$^{12}$C, measurements of neighbour light systems as $^{12}$C+$^{16}$O and $^{16}$O+$^{16}$O are scarce although relevant for the modelling of late carbon burning, oxygen burning in massive stars as well as explosive carbon burning of Type Ia supernovae[1]. Furthermore, a comprehensive picture of these alpha-conjugated systems might reveal the underlying microscopic origin of several puzzling observations which are still not fully understood such as the potential existence of clusters[2,3] or the fusion hindrance mechanism[4] affecting systems in sub-barrier fusion.

Following the successful first phases of $^{12}$C+$^{12}$C measurements with STELLA[5], the CarbOx project aims at precisely determining the astrophysical S-factor for the $^{12}$C+$^{16}$O and $^{16}$O+$^{16}$O reactions in coincidence. The key experimental on-going developments to achieve an enhanced energy and angular resolution needed to unambiguously resolve the increased complexity of the final states of these systems will be detailed and the sensitivity expected after the CarbOx upgrades will be discussed.

[1] Woosley et al. PRL 27 (1971)
[2] Fang et al. PRC 96 (2017)
[3] Taniguchi and Kimura, PRB 800 (2020)
[4] Jiang et al. PRL 93 (2004)
[5] Fruet et al. PRL 124 (2020)

Speaker: Aurelie Bonhomme (IPHC)

npa_bonhomme_public.pdf

225 Lifetime measurement of astrophysically relevant 6.793 MeV state $^{15}$O

The CNO cycle is the main energy production mechanism in stars heavier than our Sun, defining both their evolution and lifespan. The solar $\nu$-flux from the CNO cycle has been recently measured by the Borexino collaboration and it could provide an independent estimate of the solar metallicity, i.e.\ the CN abundance in the core of the sun.
The equilibrium of the CNO cycle is ruled by the $^{14}$N($p,\gamma$)$^{15}$O reaction, the slowest one of the cycle. Nevertheless, at typical hydrogen burning temperatures, unreachable by direct measurements, the extrapolations are affected by high uncertainty due to the contribution of the sub-threshold state at $E_{x} = 6.793$~MeV. One significant improvement would be to measure the lifetime of the excited state of interest. Previous attempts suggest that this lifetime lies in the sub-fs range, making it a very challenging measurement. Indeed, literature data are all affected by large uncertainties.
A new lifetime measurement was recently performed at the Legnaro National
Laboratories, INFN, using the advanced gamma-ray tracking array
AGATA combined with a DSSSD silicon detector. A $^{16}$O beam was sent
to a target of $^{3}$He implanted in a thin Au foil. In the present
contribution, preliminary experimental results will be discussed.

Speaker: Elia Pilotto (Istituto Nazionale di Fisica Nucleare - Sezione di Padova)

NPA_15Olifetime.pdf

226 Remeasuring of the $\gamma$-decay branching ratio of the Hoyle State

The triple-alpha process is one of the most fundamental processes in stellar nucleosynthesis, and in particular, the stellar production of carbon. This process entails the fusion of three helium nuclei to form an intermediate state in $^{12}$C. This intermediate state can decay back into its three constituent alpha particles or radiatively decay to form stable $^{12}$C. At temperatures between 0.1 - 2 GK, the triple-alpha reaction is almost exclusively mediated by the Hoyle state in 12C. Understanding the properties of the Hoyle state is therefore important for the modeling of the subsequent stellar evolution.

The creation of stable carbon through this process happens mainly through two available decay branches, leaving the $^{12}$C in its ground state. The radiative decay of the Hoyle state to form stable 12C proceeds mainly through gamma decay and pair production. The radiative width of the gamma-branch has been measured several times between the period 1961 to 1976 [1-7]. Most of the measurements performed up until 1976 have yielded results which are in decent agreement with one another. However, a recent measurement performed in 2019 by Kibédi et al. [8] resulted in a significantly larger radiative branching ratio ($\Gamma_{rad}/\Gamma$) compared to all previous measurements.

Given the astrophysical significance of the Hoyle state, resolving this conflict is crucial. Therefore, new measurements have been performed to reinvestigate the gamma-decay branching ratio of the Hoyle state. The experiments have been performed at the Oslo Cyclotron Laboratory through the $^{12}$C(p, p'$\gamma \gamma$)-reaction. In these experiments, the SiRi particle telescope [9] was employed to detect proton ejectiles and the OSCAR LaBr3 array was used to detect the coincident gamma-ray decays. Results from this measurement will be presented, together with the analysis method and experimental details.

Speaker: Wanja Paulsen (Department of Physics, University of Oslo, Oslo N-0316 Oslo, Norway)

wanjaPaulsen_NPA_XI.pptx

227 Jet and Extended Gas Target System for the Felsenkeller Underground Laboratory

We present a newly developed jet and extended windowless gas target system, tailored to meet the precision measurement demands of modern nuclear astrophysics. Our system can be operated either in jet or extended modes without necessitating modifications in pumping power. Real-time monitoring of a jet, facilitated by laser interferometry techniques, ensures control of target parameters during operation. Our development process involved comprehensive computational fluid dynamics simulations to optimize nozzle geometry.
Characterization of the jet target involved both absolute target thickness determination using alpha energy loss techniques and relative thickness measurements via laser interferometry. These techniques collectively ensure a comprehensive understanding and control of target parameters. Experimentally measured the areal density of the jet on the order of $10^{18}$ atoms/cm$^{2}$.
For the extended gas target setup, pressure, and temperature profiles are measured to construct the density profile of an extended gas target. Additionally, a beam calorimeter has been developed and tested to measure the beam intensity.
The setup has undergone development and testing at the Rossendorf Center and now is in the commissioning phase at the Felsenkeller underground ion accelerator laboratory. Our report will provide insight into the developments, characterization, and operational capabilities of our newly developed combined gas target system.

Speaker: Anup Yadav (Helmholtz-Zentrum Dresden Rossendorf (HZDR))

Anup_Yadav_240920.pptx

10:50 Coffee Break

Plenary Session: P: Explosive processes (4). & Neutron Capture processes (5).

Convener: György Gyürky (HUN-REN Institute for Nuclear Research)

228 Proton-Induced Reactions at the ESR Storage Ring

To understand and model element synthesis and energy budget in stars a large number of nuclear reaction cross sections must be known. For explosive stellar scenarios, like supernovae or x-ray bursts, this heavily involves nuclei beyond stability. However, due to the challenges inherent to related experiments, the lack of available experimental data in this domain is severe.

A new method for measuring cross sections of proton-induced reactions has been developed using cooled and decelerated beams at the ESR heavy ion storage ring at GSI. It enables studies of $(\mathrm{p},\gamma)$ and $(\mathrm{p},\mathrm{n})$ reactions on radioactive ions inside or close to the astrophysical Gamow window, which can deliver the necessary constraints for nuclear theory and astrophysics.

Most recently, the technique was upgraded, enabling the first successful application to a radioactive beam. This talk will give an overview of past and recent developments and results, as well as an outlook to future experiments and physics cases.

Speaker: Jan Glorius (GSI Helmholtzzentrum, Darmstadt)

229 Weak rp-process nucleosynthesis in primordial novae explosions

Classical novae are stellar thermonuclear explosions involving a white dwarf accreting material from a companion star. Early in the Galactic history, these explosions proceeded differently, mainly due to the accretion of sub-solar metallicity material onto the white dwarf. It has been proposed that these primordial nova explosions produce a different abundance pattern compared to their classical counterparts. In particular, the nuclear flows extend up to the Cu-Zn region resembling a weak rp-process, compared to classical novae which have an endpoint around Ca. We studied the nucleosynthesis in that scenario and also the impact of the nuclear physics uncertainties in the final abundance pattern, varying all the relevant reactions in the network within their uncertainty using a Monte Carlo approach. We find nuclear reactions whose uncertainties affect the production of intermediate mass nuclei under primordial-nova conditions. These reactions need to be measured experimentally at stable and radioactive beam facilities to reduce their rate uncertainties. To begin constraining these reactions, recent indirect (3He,d) transfer measurements to extract information for (p,γ) reactions using the Enge split-pole spectrograph at the Triangle Universities Nuclear Laboratory (TUNL) will be discussed.

Speaker: Thanassis Psaltis (TUNL/Duke University)

Psaltis-NPA-XI.pdf

230 Lifetime measurement of the dominant $^{22}$Na (p, γ) $^{23}$Mg resonance in novae

$^{22}$Na (T$_{1/2}$ = 2.6 y) is of high interest for space-based γ-ray astronomy because its direct observation could constrain classical nova models. Although the characteristic 1275 keV β-delayed γ decay radiation has not been observed yet, future γ-ray telescopes may detect the decay with high sensitivity. To link these observations with nova model predictions, nuclear data are needed. The $^{22}$Na(p,γ)$^{23}$Mg reaction destroys $^{22}$Na produced during a nova. In the literature, there are discrepancies of one order of magnitude in the experimentally determined strength of the E$_R$ = 204 keV resonance important at nova temperatures. This affects predictions of the ejected yield substantially.
The resonance strength can be determined by measuring the proton branching ratio and the lifetime of the corresponding E$_x$ = 7.785 MeV excited state in $^{23}$Mg.
With the Doppler-Shift Lifetime (DSL2) setup at TRIUMF-ISAC-II a new effort was started to measure the lifetime of this exited state. Excited states in $^{23}$Mg are populated by the $^{24}$Mg ($^3$He,α) $^{23}$Mg reaction with a 75 MeV $^{24}$Mg beam. Using the Doppler-Shift Attenuation Method (DSAM), deexcitation γ-rays are detected to perform line-shape analysis and infer the lifetime. This contribution will present the DSAM method and results from a preliminary measurement.

Speaker: Dr Louis Wagner (TRIUMF)

LWagner_NPA2024_Lifetime measurement of the dominant 22Na(p,g)23Mg resonance in novae.pptx

231 Magnetic mixing in AGB stars and branchings in the s-process

The nucleosynthesis process involving neutron captures during stellar helium burning, known as the s-process, contributes to roughly half of the elements heavier than iron. As for Asymptotic Giant Branch (AGB) stars, they are major producers of nuclei from Sr to Pb. Despite significant theoretical progress in recent decades, uncertainties persist in AGB models, notably regarding the mechanism responsible for the formation of the so-called $^{13}$C pocket, the main neutron source in AGB stars. Here we present recent results from new AGB stellar models considering the effects of mixing induced by magnetic fields, for the first time computed by simultaneously solving the nuclear and burning equations. We show the impact of using different mixing schemes on the branches along the s-process path and discuss the production of the long-living s-only isotope $^{205}$Pb in the light of new temperature- and density-dependent weak decay rates of $^{205}$Pb and $^{205}$Tl.

Speaker: Diego Vescovi (INAF - Osservatorio Nazionale d'Abruzzo)

Vescovi_NPA_XI.pdf

232 Probing the third r-process peak with high-resolution spectra

With the recent large-scale surveys such as APOGEE, GALAH, LAMOST, among others, our knowledge about stellar nucleosynthesis, as well as the chemical evolution and composition of the Milky Way, has been growing quickly. However, surveys have a trade-off between data volume and data quality, to allow probing the chemistry of the Galaxy as a whole. That results in some potentially interesting species being overlooked, a gap that can be filled by boutique spectroscopic studies relying on very high-quality data. In order to contribute with the understanding of how some of the heaviest elements of the periodic table behave both in terms of stellar nucleosynthesis and Galactic Chemical Evolution, we will present a study on Hf, Os, and Ir abundances using high resolution (R ~40,000), high signal-to-noise ratio stellar spectra observed with UVES at VLT. Our sample consists of 52 metal-poor (-3.5 < [Fe/H] < -1.7), C-normal red giants, presenting a large range of Eu abundances. We will discuss how our results impact the understanding of the r-process, in particular the third peak, as well as the their relationship (or absence of) with stellar kinematics.

Speaker: Arthur Alencastro Puls (Goethe University Frankfurt)

233 Numerical simulations of dynamic i-process nucleosynthesis in stars constrained by nuclear physics experiments and astrophysical observations

We present evidence that the heavy-element abundances in maybe most carbon-enhanced metal-poor stars point to i-process nucleosynthesis, at neutron densities intermediate between those of the s- and r-processes. The i process may occur in a helium convective zone that entrains hydrogen from an adjacent H-rich envelope, for example in rapidly-accreting white dwarfs, like those considered to lead to Supernova Ia explosions in the single-degenerate channel, in asymptotic giant branch (AGB) stars at low metallicities, in super-AGB stars or possibly Pop III massive stars. Our i-process nucleosynthesis simulations of multi-zone models of RAWDs and AGB stars are compared with elemental and isotopic abundance ratios measured in CEMP stars and pre-solar dust grains. The i-process path proceeds through unstable species, which have mostly only theoretical neutron-capture reaction rates from Hauser-Feshbach models. Early experimental results have already reduced the uncertainty of key (n,g) cross sections. Based on our Monte Carlo (MC) simulations, in which all rates are varied within their limits estimated from Hauser-Feshbach computations we obtained updated results on the most important future measurements. We show that in addition to accurate nuclear physics data time-dependent hydrodynamic effects of convective-reactive i-process nucleosynthesis are key to reconcile observations with model predictions.

Speaker: Falk Herwig (University of Victoria)

Herwig-NPAXI-iprocess_v2.pdf

234 Closing

Speaker: Prof. Daniel Bemmerer (HZDR)