Maria Bergemann: Chemical composition of Galactic stars in 3D NLTE

Dr. Maria Bergemann (research group leader, MPIA Heidelberg, Germany) will show us how 3D radiation hydrodynamical modeling of stellar atmospheres, including non-LTE effects, has advanced our ability to precisely determine element abundances and conclude about the chemical evolution of the Milky Way.

One of the prime questions in modern astrophysics is the origin and evolution of chemical elements. Why is the chemical composition so different for various astronomical objects, such as the Sun, Galactic stars and their planetary companions, and extragalactic stellar populations? How can one explore the full history of the evolution of elements, from the Big Bang to the present?

I will review recent progress in studying the chemical enrichment of the Milky Way galaxy. The focus of my talk will be on advances in determining stellar chemical composition, driven by novel, physically realistic models of stellar atmospheres. These models rely on the physics of non-local thermodynamic equilibrium (Non-LTE) and 3D radiation-hydrodynamics simulations of stellar convection. Combined with new data from major observational facilities, such as Keck, VLT, and TESS, these models represent a new wave in the study of stellar interiors, atmospheric structure, chemical composition, and fundamental parameters of stars.

I will summarize, in particular, how 3D NLTE modeling has advanced our understanding of the structure and evolution of the Sun, how evidence for non-standard SN Ia explosions has emerged from 3D NLTE abundances of iron-group elements, and how constraints on the properties of compact binary mergers leading to kilonovae can be obtained from observations of the heaviest r-process elements in stellar spectra. I will conclude with a brief summary of the prospects for studies of stars using 3D NLTE modeling and next-generation large spectroscopic surveys, including 4MOST and SDSS-V, space-based missions like PLATO, and 40-meter-class telescopes such as the ELT.