SNAQ November 2021

online (virtual)



Link will be provided after registration.
Camilla J. Hansen, Andreas Korn (Uppsala University, Sweden), Arūnas Kučinskas (Vilnius University), Konrad Schmidt (HZDR)


Schools on Nuclear Astrophysics Questions

Question in November 2021: How to interpret stellar spectra?

Update: Below, all talks are available as PDF for download.

Update: Congratulation to the 2 winners of our SNAQs Scientific Talk Award in recogrecognition and appreciation for giving a scientic talk at the November 2021 edition of SNAQs:

  • Borbála Cseh (Konkoly Thege Miklós Astronomical Institute, Hungary)
  • Linda Lombardo (Observatoire de Paris, France)

And thanks to all other applicants who submitted an abstract.

This is the 7th edition of a monthly, virtual school format discussing questions related to nuclear astrophysics.

Previous events:
Next event:  

We plan to organize a new event of SNAQs always on the 2nd Wednesday in each month with a break in summer. SNAQs will last about 3.5 hours, including breaks, with lectures and scientific talks around a given question in nuclear astrophysics. Lectures will be held by senior researchers and scientific talks preferably by young researchers, as master and PhD students. Further, SNAQs will put a special focus on the interaction between participants to allow young scientists networking even if traveling to schools, workshops and conferences is not an option.

SNAQs will join the community of schools related to nuclear astrophysics that partner with ChETEC-INFRA:

  • Carpathian Summer School of Physics (well established)
  • European Summer School on Experimental Nuclear Astrophysics (well established)
  • Intercontinental School on Nuclear Astrophysics (new)
  • International school on nuclear physics, neutron physics and applications (well established)
  • Nuclear Physics in Astrophysics School (new)
  • Rußbach School on Nuclear Astrophysics (well established)
  • School on observations and spectroscopic tools (new)

The aim of this community is to give all students and young researchers the same, multidisciplinary knowledge about nuclear astrophysics. SNAQs will support this idea and strengthen the community of schools by providing a frequent lecture series to train and educate the next generation of scientist with knowledge across the three types of infrastructures used by nuclear astrophysicists:

  • astronuclear laboratories supplying reaction data,
  • supercomputer facilities performing stellar structure and nucleosynthesis computations, and
  • telescopes and mass spectrometers collecting elemental and isotopic abundance data.

Those infrastructures are networked by ChETEC-INFRA, Chemical Elements as Tracers of the Evolution of the Cosmos - INFRAstructures for Nuclear Astrophysics, a new European starting community of 32 partner institutions.

We are looking forward to meet you at the sixth SNAQ.

SNAQ November 2021 organizers SNAQs organizing committee
  • Camilla Juul Hansen (TU Darmstadt, Germany)
  • Andreas Korn (Uppsala University, Sweden)
  • Arūnas Kučinskas (Vilnius University, Lithuania)
  • Rosanna Depalo (Università degli Studi di Milano, Italy)
  • Camilla Juul Hansen (TU Darmstadt, Germany)
  • Marcel Heine (Hubert Curien Pluridisciplinary Institute, France)
  • Ann-Cecilie Larsen (University of Oslo, Norway)
  • Andreas Korn (Uppsala University, Sweden)
  • Arūnas Kučinskas (Vilnius University, Lithuania)
  • Mohamad Moukaddam (University of Strasbourg, France)
  • Sara Palmerini (University of Perugia, Italy)
  • Gianluca Pizzone (Laboratori Nazionali del Sud, Italy)
  • Konrad Schmidt (Helmholtz-Zentrum Dresden-Rossendorf, Germany)
  • Olivier Sorlin (Grand Accélérateur National d'Ions Lourds, France)
  • Livius Trache (Horia Hulubei National Institute for Physics & Nuclear Engineering, Romania)
  • Aurora Tumino (Kore University of Enna, Italy)

Guidelines for participants of SNAQs

Please, …
… rename yourself in the Zoom sessions to match your registration name and institution – this will serve as your “nametag”.
… mute your microphone during talks.
… use the public chat only for questions related to the lecture; for discussions, please use the private chat.
… write your questions in the chat – due to the high number of participants, a moderator will read a selection of questions but can choose a limited number only.
… use breakout rooms to talk and chat to each other in smaller groups. Breakout rooms will be available during coffee breaks and participants can choose rooms freely.
… behave professionally and respectfully.
… follow ethical standards as professional integrity and honesty.
… foster a welcoming and inclusive work environment.


There are minutes attached to this event. Show them.
    • 1:45 PM
      Zoom available
    • 1
      Speaker: Konrad Schmidt (HZDR)
    • 2
      Introduction to observational schools in 2022

      We will provide a brief overview on the planned CHETEC-INFRA Observation School and the planned NPA School in 2022, both schools including observation sessions with the Nordic Optical Telescope (NOT).

      Speaker: Andreas Korn (Uppsala University, Sweden)
    • 3
      Tools and techniques for modelling stellar spectra in 1D/LTE

      First lecture

      Speaker: Bertrand Plez (University of Montpellier, France)
    • 4
      Moderated questions
      Speaker: Camilla J. Hansen (TU Darmstadt, Germany)
    • 5
      Tools and techniques for modelling stellar spectra beyond 1D/LTE

      Second lecture

      Speaker: Andy Gallagher (Leibnitz Institute for Astrophysics, Germany)
    • 6
      Moderated questions
      Speaker: Arūnas Kučinskas (Vilnius University, Lithuania)
    • 4:00 PM
      Coffee break and breakout sessions

      Breakout rooms are available to (1) very briefly introduce yourself, (2) talk about the lectures, (3) clarify lecture items, and (4) phrase questions for the round table discussion.

      Afterwards, questions can be written in the chat of the main Zoom room. Please tag questions related to lecture 1 with L1 and questions related to lecture 2 with L2. Moderators can only choose a limited number of questions to be discussed at the round table discussion.

      This session also povides the opportunity to establish contacts that can be continued using the private chat. Networking is an important tool not only in science.

    • 7
      Tracing the slow neutron capture process in AGB stars using Ba star abundances

      Barium (Ba) stars are polluted by material enriched in the slow neutron capture (s-process) elements synthesized in the interior of their former asymptotic giant branch (AGB) companion star, which is now a white dwarf. By comparing AGB nucleosynthesis models with different s-process elemental abundances derived from the largest homogeneous set of Ba giant star observations we can reach a better understanding of the s process in AGB stars. All the computed hs-type (La, Ce, and Nd) to ls- type (Y and Zr) element ratios show a clear increasing trend with decreasing metallicity. This trend is predicted by low-mass AGB models in which 13C is the main neutron source. We selected a sample of 28 Ba stars for which both self-consistent spectroscopic observation and analysis are available and stellar mass determinations, via positioning the star on the HR diagram and comparing with evolutionary tracks. For this sample stars we considered both previously (Y, Zr, Ce, and Nd) and recently derived (Rb, Sr, Nb, Mo, Ru, La, Sm, and Eu) elemental abundances. Then, we performed a detailed comparison of these s-process elemental abundances to different AGB nucleosynthesis models from the Monash and the FRUITY theoretical data sets. We simplified the binary mass transfer by calculating dilution factors to match the [Ce/Fe] value of each star when using different AGB nucleosynthesis models, and we then compared the diluted model abundances to the complete Ba star abundance pattern. Our comparison confirms that low mass (with initial masses roughly in the range 2–3 MSun), non-rotating AGB stellar models with 13C as the main neutron source are the polluters of the vast majority of the considered Ba stars, although some stars may represent the signature of a physical (e.g., mixing) and/or nucleosynthetic process that is not represented in the set of models considered here.

      Speaker: Borbála Cseh (Konkoly Thege Miklós Astronomical Institute, Hungary)
    • 8
      Moderated questions
      Speaker: Andreas Korn (Uppsala University, Sweden)
    • 9
      Evidence for rotation and mixing in a sample of young massive giant stars

      In the search of a sample of metal-poor bright giant stars using Strömgren photometry, we serendipitously found a sample of 26 young (ages younger than 1 Gyr) metal-rich giants, with masses between 2.5 and 6 solar masses. Ten of these stars also rotate rapidly (vsini > 10 km/s). The high stellar masses suggest that these stars were of spectral type A to B when on the main sequence. This evolutionary stage is not very well characterised by observations so far because of the short time spent by stars in this phase. The discovery of this sample of giant stars therefore allows us to study this evolutionary stage directly, and to compare their abundance pattern to that of main-sequence A and B stars. Moreover, it is an opportunity for testing the predictions of stellar evolutionary models in terms of the evolution of chemical abundances and rotational velocities.
      In this talk I will present how we derived the chemical abundances for 16 elements (C, N, O, Mg, Al, Ca, Fe, Sr, Y, Ba, La, Ce, Pr, Nd, Sm, and Eu) taking into account the effect of stellar rotation. I will also present the results we obtained and how they compare to the predictions of stellar evolution models.

      Speaker: Linda Lombardo (Observatoire de Paris, France)
    • 10
      Moderated questions
      Speaker: Andreas Korn (Uppsala University, Sweden)
    • 11
      Round table discussion

      Questions that were compiled in the chat during and after lectures and breakout session will be answered and discussed.