Related papers: Quantitative spectroscopy of B-type supergiants
A new model atom of nitrogen was developed using the energy levels of N I from laboratory measurements and also predicted in atomic structure calculations and the most up-to-date atomic data for computing radiative and collisional rates of…
Aluminium plays a key role in studies of the chemical enrichment of the Galaxy and of globular clusters. However, strong deviations from LTE (non-LTE) are known to significantly affect the inferred abundances in giant and metal-poor stars.…
We present accurate element abundance patterns based on the non-local thermodynamic equilibrium (non-LTE, NLTE) line formation for 14 chemical elements from He to Nd for a sample of nine A9 to B3 type stars with well determined atmospheric…
Context. Observationally constraining the atmospheric temperature-pressure (TP) profile of exoplanets is an important step forward for improving planetary atmosphere models, further enabling one to place the detection of spectral features…
Carbon abundances in late-type stars are important in a variety of astrophysical contexts. However C i lines, one of the main abundance diagnostics, are sensitive to departures from local thermodynamic equilibrium (LTE). We present a model…
We perform non-LTE calculations of lithium in late-type stars for a wide range of stellar parameters, including quantum mechanical cross-sections for collisions with neutral hydrogen and the negative hydrogen ion. Non-LTE abundance…
A new grid of detailed atmosphere model spectra for hot and moderately cool subdwarf stars is presented. High-resolution spectra and synthetic photometry are calculated in the range from 1000{\AA} to 10,000{\AA} using Non-LTE fully…
In this review we discuss possible systematic errors inherent in classical 1D LTE abundance analyses of late-type stars for the light elements (here: H, He, Li, Be and B). The advent of realistic 3D hydrodynamical model atmospheres and the…
We investigate the synthesis of the Balmer and Paschen lines of the quiet Sun, using both classical semi-empirical and theoretical model atmospheres, modern line broadening theory and non-LTE line-formation. The computations alleviate…
We investigate the ability of both LTE and Non-LTE models to fit the near UV band absolute flux distribution and individual spectral line profiles of three standard stars for which high quality spectrophotometry and high resolution…
Medium resolution J-band spectroscopy of individual red supergiant stars is a promising tool to investigate the chemical composition of the young stellar population in star forming galaxies. As a continuation of recent work on iron and…
Mg is often traced in late-type stars using lines of neutral magnesium, which is expected to be subject to departures from LTE. The astrophysical importance of Mg as well as its relative simplicity from an atomic physics point of view,…
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…
Non-LTE calculations are performed for NII in stellar atmospheric models appropriate to main sequence B-stars to produce new grids of equivalent widths for the strongest NII lines commonly used for abundance analysis. There is reasonable…
Context. Obtaining precise stellar and wind properties and abundance patterns of massive stars is crucial to understanding their nature and interactions with their environments, as well as to constrain their evolutionary paths and…
The current status of NLTE model atmosphere calculations of A type stars is reviewed. During the last decade the research has concentrated on solving the restricted NLTE line formation problem for trace elements assuming LTE model…
Context: The solution of the nonlocal thermodynamical equilibrium (non-LTE) radiative transfer equation usually relies on stationary iterative methods, which may falsely converge in some cases. Furthermore, these methods are often unable to…
We present the results obtained using spectroscopic data taken with the intermediateresolution Multi Unit Spectroscopic Explorer (MUSE) of B and A-type supergiants and bright giants in the Sculptor Group galaxy NGC 300. For our analysis, a…
Quantitative analyses of extreme helium stars to date face the difficulty that theory fails to reproduce the observed helium lines in their entirety, wings and line cores. Here, we demonstrate how the issues can be resolved using…
Structures in circumstellar matter reflect both fast processes and quasi-equilibrium states. A geometrical diversity of emitting circumstellar matter is observed around evolved massive stars, in particular around B[e] supergiants. We…