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%,...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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....
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...
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...
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...
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....
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...
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...
$^{29}$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...
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...
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...
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...
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...
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 ${}^{17}\mathrm{O}(\alpha,n){}^{20}\mathrm{Ne}$...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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,...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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)...
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...
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....
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
$^{205}$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...
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...
