Related papers: Review: progress in NLTE calculations and their ap…
M dwarfs are key targets for high-resolution spectroscopic analyses due to a high incidence of these stars in the solar neighbourhood and their importance as exoplanetary hosts. Several methodological challenges make such analyses…
New numerical models of line-driven stellar winds of late O stars are presented. Statistical equilibrium (NLTE) equations of the most abundant elements are solved. Properly obtained occupation numbers are used to calculate consistent…
In this paper we discuss numerical methods and algorithms for the solution of NLTE stellar atmosphere problems involving expanding atmospheres, e.g., found in novae, supernovae and stellar winds. We show how a scheme of nested iterations…
Europium plays a key role in studies of nucleosynthesis in the rapid (r-) process of neutron capture nuclear reactions and the evolution of the r-process element abundances in galaxies. We refine the method for analyzing the Eu~II lines in…
Context. B-type supergiants are versatile tools to address various astrophysical topics, ranging from stellar atmospheres over stellar and galactic evolution to the cosmic distance scale. Aims. A hybrid non-LTE approach - line-blanketed…
It is well known that cool star atmospheres depart from local thermodynamic equilibrium (LTE). Accurate abundance determination requires taking those effects into account, but the necessary non-LTE calculations are often lacking. Our goal…
Hydrodynamical (or 3D) and non-local thermodynamic equilibrium (NLTE) effects are known to affect abundance analyses. However, there are very few observational abundance testsof 3D and NLTE models. We developed a new way of testing the…
A comprehensive model atom was constructed for C I using the most up-to-date atomic data. We evaluated non-local thermodynamical equilibrium (NLTE) line formation for neutral carbon in classical 1D models representing atmospheres of…
We present LTE and NLTE atmospheric models of a star with solar parameters, and study the effect of treating many thousands of Iron group lines out of LTE on the computed atmospheric structure, overall absolute flux distribution, and the…
We have developed a model atom for Cu with which we perform statistical equilibrium computations that allow us to compute the line formation of Cu I lines in stellar atmospheres without assuming Local Thermodynamic Equilibrium (LTE). We…
Accurate atomic data have become available in the recent past due to the demands of astrophysics and fusion research. We report on the impact of such data on non-LTE line-formation calculations for CNO in early-type stars. Considerable…
Non-local thermodynamic equilibrium (NLTE) line formation for neutral and singly-ionized iron is considered through a range of stellar parameters characteristic of cool stars. A comprehensive model atom for Fe I and Fe II is presented. Our…
In the past years we have made great efforts to reduce the statistical and systematic uncertainties in stellar parameter and chemical abundance determinations of early B-type stars. Both the construction of robust model atoms for non-LTE…
In the current era of stellar spectroscopic surveys, synthetic spectral libraries are the basis for the derivation of stellar parameters and chemical abundances. In this paper, we compare the stellar parameters determined using five popular…
We present non-Local Thermodynamic Equilibrium (non-LTE) calculations for neutral carbon spectral line formation, carried out for a grid of model atmospheres covering the range of late-type stars. The results of our detailed calculations…
We introduce the classical stellar atmosphere problem and describe in detail its numerical solution. The problem consists of the solution of the radiation transfer equations under the constraints of hydrostatic, radiative and statistical…
The dominant site(s) of the $r$-process are a subject of current debate. Ejecta from $r$-process enrichment events like kilonovae are difficult to directly measure, so we must instead probe abundances in metal-poor stars to constrain…
Historically, various methods have been employed to understand the origin of the elements, including observations of elemental abundances which have been compared to Galactic Chemical Evolution (GCE) models. It is also well known that 1D…
We describe our method to construct line blanketed NLTE model atmospheres for hot stars. We employ the Accelerated Lambda Iteration and use statistical methods to deal with metal line blanketing.
Early chemical enrichment processes can be revealed by the careful study of metal-poor stars. In our Local Group, we can obtain spectra of individual stars to measure their precise, but not always accurate, chemical abundances.…