Seminar: 3D non-LTE elemental abundance measurements of late-type stars

  • Date: –15:00
  • Location: Ångströmlaboratoriet, Lägerhyddsvägen 1 Hjorter’s room (Å73101)
  • Lecturer: Anish Amarsi
  • Contact person: Sofia Ramstedt
  • Seminarium

Stars leave their signatures on the light that they emit, in the form of spectral lines. These signatures can be decoded to reveal the fundamental parameters and chemical compositions of stars, which can then shed light on the structure and evolution of stars, and of the Galaxy. However, such spectroscopic analyses are heavily model dependent. Shortcomings in the models often restrict the accuracy of the final results. For late-type stars like our Sun, two of the main problems in present-day methods are that they assume that stellar atmospheres are a) one-dimensional (1D) and hydrostatic, and b) satisfying local thermodynamic equilibrium (LTE).

I shall discuss our efforts to relax both assumptions simultaneously, by carrying out detailed 3D non-LTE radiative transfer post-processing of 3D hydrodynamic model stellar atmospheres. I shall go over the implications on the solar chemical composition and the solar abundance problem, and present recent results on carbon, oxygen, and iron abundances in a sample of around 200 Milky Way disk and halo stars. Finally, I shall describe our efforts to implement these improved models into the analysis pipelines of planned and ongoing large stellar surveys of millions of stars, including GALAH and 4MOST.