Letters of Intent received in 2019

LoI 2021-2063
GA Focus Meeting: Stellar synthetic spectra to study stellar populations in the Gaia era

Date: 18 August 2021 to 19 August 2021
Category: Focus meetings (GA)
Location: Busan, Korea, Rep of
Contact: Piercarlo Bonifacio (Piercarlo.Bonifacio@obspm.fr)
Coordinating division: Division G Stars and Stellar Physics
Other divisions:
Co-Chairs of SOC: Bonifacio (Observatoire de Paris, CNRS)
Hubrig (Leibniz-Institut für Astrophysik Potsdam)
Chair of LOC: None (None)



Model atmospheres
Synthetic spectra and synthetic colours
Stellar populations
Atmospheric parameters and chemical abundances
Homogeneous analysis of extremely large amounts of data
Inter-calibration of different surveys



We are witnessing a revolution in our understanding of the structure, the
history and the evolution of our Galaxy and Local Group galaxies thanks to the
Gaia mission and the many wide angle photometric surveys conducted both from
space and from the ground, as well as the spectroscopic surveys conducted
mainly from the ground. The modelling of the stellar atmospheres and of their
emerging radiation is crucial for the interpretation of the photometric and
spectroscopic data already collected and that will be collected in the coming

There have been very important advances in the modelling of stellar atmospheres
and their emerging spectra in the past ten years. The three-dimensional
modelling of the stellar atmospheres has been tackled successfully in many
cases. Line radiative transfer has been computed relaxing the assumption of
Local Thermodynamic Equilibrium (LTE) for many atoms both in one-dimensional
(1D) and three-dimensional (3D) model atmospheres.

The purpose of the Focus Meeting we propose, is to bring together the community
that has been making these significant advances, often working in parallel.
This will allow us to give to everybody an overview of the activities on these
topics that are taking place in the different parts of the world, and an
opportunity to build new synergies between the different groups.

Among the questions that we wish to tackle are:
What developments do we need for non-LTE modelling ? What developments do we
need for 3D model atmospheres ? How to efficiently compute large grids of
model atmospheres and synthetic spectra (by large we mean more than 10^4
models/spectra ) ?
How to validate the realism of synthetic spectra and
colours ?
What is the role of relatively small samples of stars with
extremely high quality observations ?
How to best extract astrophysical information from extremely large
collections of data ?

We wish to dedicate this Focus Meeting to the memory of Fiorella Castelli,
who has greatly contributed to these topics.

Our working group presently includes, besides the co-chairs,˘in alphabetical order): F. Allard ((Univ. Lyon, CNRS, France), A. Amarsi (MPIA, Germany),S. Ćalıșkan (Ankara University, Turkey), R. Collet (Aarhus University, Denmark), S. Daflon (Observatório Nacional-MCTIC, Brazil), R. L. Kurucz (CfA, USA), H. Li (National Astronomical Observatories, China), L. Mashonkina (Institute of Astronomy, Russian Academy of Sciences, Russia), P. Molaro (INAF, OA Trieste, Italy), A. Mucciarelli (Univ. di Bologna, Italy), B. Plez (Univ. Montpellier, France), L. Sbordone (ESO, Chile), T. Sivarani(Indian Institute of Astronomy and Astrophysics, India), M. Steffen (Leibniz-Institut für Astrophysik Potsdam, Germany)