3D non-LTE calculations of stellar spectra

SNIC 2018/3-465


SNIC Medium Compute

Principal Investigator:

Paul Barklem


Uppsala universitet

Start Date:


End Date:


Primary Classification:

10305: Astronomy, Astrophysics and Cosmology

Secondary Classification:

10302: Atom and Molecular Physics and Optics




Stars leave their fingerprints on the light that they emit, in the form of absorption and emission features. Decoding this information to infer stellar parameters and chemical compositions is of key interest to astronomers. However, such measurements are heavily model dependent, and for late-type stars like the Sun the accuracy of spectroscopic models is often limited by the use of one-dimensional (1D) hydrostatic model atmospheres and the assumption of local thermodynamic equilibrium (LTE). Our group works actively on addressing the systematic errors associated with the 1D non-LTE spectroscopic method. For this project, we shall combine our atomic physics (e.g. Barklem 2016, 2018) and radiative transfer expertise (e.g. Amarsi, Nordlander, Barklem, et al., 2018) to perform spectral line formation calculations in 3D inhomogeneous hydrodynamic stellar atmospheres under non-LTE conditions, using our 3D non-LTE code BALDER. We shall then compare the resulting synthetic spectra to observed stellar spectra, to perform the most accurate stellar spectroscopic analyses of late-type stars (like the Sun) to date. References: Amarsi, A. M., T. Nordlander, P. S. Barklem, M. Asplund, R. Collet, and K. Lind. “Effective Temperature Determinations of Late-Type Stars Based on 3D Non-LTE Balmer Line Formation.” Astronomy and Astrophysics 615 (July 2018): A139. Barklem, Paul S. “Accurate Abundance Analysis of Late-Type Stars: Advances in Atomic Physics.” The Astronomy and Astrophysics Review 24, no. 1 (May 31, 2016): 1–54. Barklem, P. S. “Excitation and Charge Transfer in Low-Energy Hydrogen Atom Collisions with Neutral Oxygen.” Astronomy & Astrophysics 610 (February 1, 2018): A57.