IWR News New IWR Member: Dr. Andreas Sander

Dr. Andreas Sander is an astrophysicist working on modelling the outermost layers of stars, the so-called stellar atmospheres. Focussing in particular on hot and massive stars, the engines of our Universe, such models need to account for the inherent, radiation-driven stellar winds with further physical and numerical complexity being introduced by the absence of any local thermodynamic equilibrium, typically assumed for solar-like and cooler stars. Radiative transfer plays a crucial role to accurately predict the spectral appearance of stars as light is the most important source of information we can get from them. Building on the foundations of Kirchhoff und Bunsen, decoding starlight into physical quantities marks a fundamental, ongoing challenge in modern astrophysics which for hot, massive stars can only be tackled with the help of modern computational simulations.

Dr. Sander started his career at Potsdam University in Germany where he did his Diploma thesis in 2010 on the quantitative spectral analysis of carbon-rich Wolf-Rayet stars, a specific class of evolved massive stars with emission-line dominated spectra. Intrinsically requiring to connect spectroscopy and numerical modelling, Dr. Sander became an expert in radiative transfer and hydrodynamics in stellar atmospheres during his PhD, which he finished in 2016. As as postdoctoral researcher, Dr. Sander moved to Armagh Observatory and Planetarium (AOP), Northern Ireland, in 2018 to explore the theoretical fundament of radiation-driven winds with his own line of atmosphere modelling. After being awarded the independent Öpik Research Fellowship at the AOP in 2020, Dr. Sander successfully applied for the DFG Emmy Noether programme, which in 2021 took him back to Germany, where he started his own junior research group at Heidelberg University.

To uncover the properties and impact of massive stars accross cosmic time, the work of Dr. Sander and his group combines scientific computing with observational and theoretical astrophysics as well as fundamental atomic physics. With their unique expertise in the German and international astrophysical landscape, the group has quickly established themselves in the field of massive star research with many international collaborators and major involvements in organized programmes (e.g., X-Shooting ULLYSES, BLOeM, SDSS-V, OCEANS). Among the primary goals of Dr. Sander's research group are advancing the theoretical understanding of radiation-driven winds and establishing a new generation of quantitative spectroscopy for hot, massive stars.