Welcome

• Konrad Schmidt (HZDR, Germany)

Room: virtual

ChETEC-INFRA Observation School

• Andreas Korn (Uppsala University, Sweden)

Room: virtual

From starlight to spectra — Observations for stellar abundance determinations

• Heidi Korhonen (ESO, Chile)

Room: virtual First lecture on astronomical observations for stellar abundance analysis

Moderated questions

• Andreas Korn (Uppsala University, Sweden)

Room: virtual

From idea to science - The path to stellar abundance determinations

• Andreas Koch-Hansen (University of Heidelberg, Germany)

Room: virtual Second lecture on methods and tools for stellar abundance analysis

Moderated questions

• Arūnas Kučinskas (Vilnius University, Lithuania)

Room: virtual

Breakout session Room: virtual Small groups of up to 5 participants are assigned to breakout rooms 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.

The chemical composition of very young open clusters

• Martina Baratella (University of Padova, Italy)

Room: virtual In the last 15 years, several investigations seem to indicate an anomalous behaviour of young Galactic open clusters, which includes (but is not limited to) sub-solar iron (Fe) abundances of the systems in the solar neighbourhood, extreme and unexpected barium (Ba) enhancements, and super-solar abundances of some atomic species (e.g., ionised chromium). Recently, different independent studies have demonstrated that in such young stars, the higher levels of stellar activity can alter the spectral line formation and, consequently, the derived abundances. These results have drawn the attention to the necessity to revise the spectroscopic analysis technique. In this talk I will present a new spectroscopic approach (based mainly on Ti lines) developed to overcome the effects of the increased stellar activity that affects the analysis of very young (ages less than 200 Myr) stars. Moreover, I will present the preliminary results of my study on the abundances of the s−process elements (Cu, Sr, Y, Zr, Ba, La and Ce) and their time evolution. I will discuss the results and the scientific implications on stellar properties and Galactic evolution models.

Moderated questions

• Gabriele Cescutti (Astronomical Observatory of Trieste, Italy)

Room: virtual

Extreme r-process enhanced stars in the Fornax dwarf spheroidal galaxy

• Moritz Reichert (Technical University of Darmstadt, Germany)

Room: virtual There exist still open questions about the r-process and very rare r-process enhanced stars may hold the key to answer them. We analyzed three newly identified r-II stars that are members of the dwarf spheroidal galaxy Fornax. These special stars are relatively metal-rich and contain the highest amount of the r-process element europium ever observed. In addition, their membership to the dwarf galaxy is underlined by their low α-element abundances. The high amount of r-process elements even allowed the element lutetium to be measured for the first time in a dwarf spheroidal galaxy. The sheer existence of the stars is remarkable because they proof that an extreme r-process enhancement is not only a feature of the lightest galaxies, but that it is also found in the heaviest dwarf galaxies. Due to the extreme r-process enhancement, the stars open new opportunities and insights into the r-process site in these very distant galaxies. We have estimated the necessary ejected europium mass per r-process event and conclude that one r-process event is sufficient for such an extreme enhancement and the ejected mass is in agreement with previous findings. In addition, it was possible to link the birth of the stars, and thus the r-process event, with a recent star formation activity of Fornax ∼ 4 Gyr ago. This ultimately made speculations about the responsible r-process event possible.

Moderated questions

• Gabriele Cescutti (Astronomical Observatory of Trieste, Italy)

Room: virtual

Probing stellar abundances of S-type stars in the Gaia era

• Shreeya Shetye (Université Libre de Bruxelles, Belgium)

Room: virtual S-type stars are late-type giants enhanced with s-process elements originating either from nucleosynthesis during the Asymptotic Giant Branch (AGB) or from a pollution by a binary companion. The former are called intrinsic S stars, and the latter extrinsic S stars. The intrinsic S stars are on the AGB and have undergone third dredge-up events. The atmospheric parameters of S stars are more numerous than those of M-type giants (C/O ratio and s-process abundances affect the thermal structure and spectral synthesis), and hence they are more difficult to derive. These atmospheric parameters are also entangled within each other and the S stars’ spectra are dominated by molecules. Despite the challenges involved in analyzing the S stars, they are ideal candidates to investigate AGB s-process nucleosynthesis. In my talk I will present my novel methodology that combines high-resolution spectroscopic data of S stars with the Gaia early data release 3 parallaxes and with the MARCS model atmospheres for S-type stars to derive their effective temperature, surface gravity, and luminosity. These parameters not only allow us to locate the intrinsic and extrinsic S stars in the Hertzsprung-Russell (HR) diagram but also allow the accurate abundance analysis of the s-process elements. I will further present how these stellar abundances led to interesting insights into the AGB nucleosynthesis like (I) the use of zirconium-niobium pair to distinguish extrinsic from intrinsic stars, (II) the first time derivation of technetium abundances helping us to probe the AGB evolution, and (III) the comparison between AGB nucleosynthesis predictions and observations.

Moderated questions

• Gabriele Cescutti (Astronomical Observatory of Trieste, Italy)

Room: virtual

Round table discussion Room: virtual Questions that were compiled in the chat after the breakout session will be answered and discussed