High-precision spectroscopy and fundamental parameters of cool stars

Maria Bergemann

Max Planck Institute for Astrophysics/HIA

Spectroscopic observations of individual low-mass stars have shaped our understanding of Galactic evolution. However, information extracted from stellar spectra is not strictly-speaking 'observational', but heavily relies upon models, which describe physical properties of stellar surfaces. I will review the present status of stellar atmosphere modeling for cool FGK-type stars, starting from the simplest classical, yet still widely-used, 1D LTE models and introducing new mean 3D NLTE approach. I will discuss whether these models, when compared to observed spectra, are able to recover physically realistic values of effective temperature, surface gravity, and chemical composition, in particular abundances of heavy elements. Furthermore, I will show that improvements in modeling stellar atmospheres have interesting consequences for the determination of masses, ages, and spectroscopic distances to stars.