Related papers: Iron abundances from optical Fe III absorption lin…
We present accurate methods of abundance determination based on the non-local thermodynamic equilibrium (NLTE) line formation for carbon, oxygen, calcium, titanium, and iron in the atmospheres of BAF-type stars. For C I-II, O I, Ca I-II,…
Optical CCD spectra are used to determine the Fe abundances at several positions inside seven bright Galactic HII regions. The observed [FeIII] line ratios are compared with the predictions of different sets of collision strengths and…
We investigate the feasibility of the Si I infrared (IR) lines as Si abundance indicators for giant stars. We find that Si abundances obtained from the Si I IR lines based on the local thermodynamic equilibrium (LTE) analysis show large…
We present new ultra-metal-poor (UMP) stars parameters with [Fe/H]<-4.0 based on line-by-line non-local thermodynamic equilibrium (NLTE) abundances using an up-to-date iron model atom with a new recipe for non-elastic hydrogen collision…
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…
Extensive statistical-equilibrium calculations on neutral sulfur and zinc were carried out, in order to investigate how the non-LTE effect plays a role in the determination of S and Zn abundances in F, G, and K stars. Having checked on the…
Although anomalous surface abundances are often observed in A-type main-sequence stars (known as chemically peculiar stars; e.g., metallic line stars or Am stars), our understanding about the behavior of aluminium is still insufficient.…
Aluminium abundances of B-type stars were spectroscopically determined in order to get information about the galactic gas composition at the time of their formation. For this purpose, two AlII lines at 6243 and 4663A were employed. The…
Modern spectroscopy of early-type stars often aims at studying complex physical phenomena. Comparatively less attention is paid to identifying and studying the "normal" A- and B-type stars and testing how the basic atomic parameters and…
We report the detection of several absorption lines of neutral phosphorus (P, Z=15) in archival near ultraviolet spectra obtained with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. We derive phosphorus…
Stellar abundances of beryllium are useful in different areas of astrophysics, including studies of the Galactic chemical evolution, of stellar evolution, and of the formation of globular clusters. Determining Be abundances in stars is,…
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…
The atmospheric parameters and iron abundance of the Sloan Digital Sky Survey (SDSS) spectrophotometric standard star BD +17 4708 are critically examined using up-to-date Kurucz model atmospheres, LTE line formation calculations, and…
We present a new model atom of Zn I-II based on the most up-to-date photoionisation cross-sections, electron-impact excitation rates, and rate coefficients for the Zn I + H I and Zn II + H- collisions. The latter were calculated using the…
We present observations of the Be II 313.0 nm resonance doublet in 14 halo and old disk stars with metallicities ranging from [Fe/H]=-0.4 to about -3.0 obtained with the CASPEC spectrograph of the ESO 3.6m telescope at a FWHM about 8.6 km/s…
We aim to provide new empirical clues about macroturbulent spectral line broadening in O- and B-type stars to evaluate its physical origin. We use high-resolution spectra of ~430 stars with spectral types in the range O4-B9 (all luminosity…
To analyse stellar populations in galaxies a widely used method is to apply theoretically derived responses of stellar spectra and line indices to element abundance variations, hereafter referred to as response functions. These are applied…
We carried out a homogeneous abundance study for various elements, including $\alpha$-elements, iron peak elements and $n$-capture elements for 35 metal-poor stars with a wide metallicity range ($-3.0\lesssim$[Fe/H]$\lesssim-0.5$).…
We study the formation of B I lines in a grid of cool stellar model atmospheres without the assumption of local thermodynamic equilibrium (LTE). The non-LTE modelling includes the effect of other lines blending with the B I resonance lines.…
We present an analysis of the subdwarf O star Feige 67 with a fully metal-line blanketed NLTE model atmosphere based on high-resolution Far-UV (912-2000 A) and Near-UV (2000-3400 A) spectra from new ORFEUS II echelle observations and the…