Improving spectroscopic models for more accurate stellar parameters and chemical compositions

Mittwoch, 14. August 2019, 14:00 - 15:30
Veranstaltungsort* Bibliothek
Improving spectroscopic models for more accurate stellar parameters and chemical compositions
Stars leave their fingerprints on the light that they emit, in the form of
absorption and emission spectral features.  Decoding this information to infer
stellar parameters and chemical compositions is of key interest to astronomers.
However, such analyses are heavily model dependent: for late-type stars like
our Sun the accuracy of standard methods can be limited by the use of
one-dimensional (1D) hydrostatic model atmospheres, and the assumption of local
thermodynamic equilibrium (LTE).  Recently it has become feasible to relax both
assumptions simultaneously, i.e. to perform so-called 3D non-LTE stellar
spectroscopy, using 3D (magneto-)hydrodynamic stellar atmosphere simulations,
and non-LTE radiative transfer post-processing; the latter being based on
detailed atomic models that utilise physically-motivated collisional recipes.
In this talk I shall review the physics of this more realistic method.  I shall
then discuss the solar chemical composition in light of these developments,
before presenting recent results on carbon, oxygen, and iron abundances in the
Milky Way disk and halo populations, including an examination of C/O in
exoplanet host stars.  Finally, I shall describe our efforts to implement these
improved spectroscopic models into the analysis pipelines of planned and
ongoing large stellar surveys of millions of stars, including GALAH and 4MOST.


: Dr. Anish Amarsi, MPI Heidelberg