Abstract

Invited Talk - Splinter Computational

Thursday, 12 September 2024, 14:00   (S26)

The present and future of expanding non-LTE stellar atmospheres for hot stars

Andreas Sander
ZAH/ARI, Universität Heidelberg

The outermost layers of a star are referred to as the stellar atmosphere. The light that reaches us on Earth is emitted from this transition layer that connects the optically thick interior of the star to the comparably low-density interstellar medium layers. To quantitatively interpret and predict observed spectra and extract the physical parameters of stars, a realistic physical and numerical model of the stellar atmosphere is required. In particular for hot stars, this is a challenging task as their atmospheres are not in local thermodynamic equilibrium. Moreover, the presence of a stellar wind alters the structure of the atmosphere and can change the observed spectral features. Yet, hot and massive stars are shaping the evolution of galaxies since the very first generation of stars as they not only breed and release nuclear processed material, but also dominate the kinematic and ionizing feedback of young stellar populations. Many fundamental properties of hot stars are only accessible via spectroscopy, making sophisticated non-LTE atmosphere models an essential tool in modern astrophysics. In this talk, I will provide an overview of the current state of the field with respect of atmosphere models of hot stars. In particular, I will focus on expanding, non-LTE atmosphere models. Reviewing the basics and capabilities of PoWR, a leading code in the field, I will present the underlying assumptions and involved numerical techniques, and provide a brief overview of the manifold empirical and theoretical applications, ranging from quantitative spectroscopy to the theoretical study of radiation-driven winds. Finally, I will give an outlook on current observational challenges and theoretical insights from 2D and 3D simulations raising a new need to reconsider some of the current paradigms.