相关论文: NLTE spectral analysis of the intermediate helium-…

We have constructed a comprehensive grid of 1540 metal line-blanketed, NLTE, plane-parallel, hydrostatic model atmospheres for the basic parameters appropriate to early B-type stars. The BSTAR2006 grid considers 16 values of effective…

The formation of sdBs is still puzzling, as is the chemical composition of their atmospheres. While helium and other light elements are depleted relative to solar values, heavy elements are highly enriched. Diffusion processes in the hot,…

The negative hydrogen ion H$^-$ is, almost without exception, treated in local thermodynamic equilibrium (LTE) in the modelling of F, G, and K stars, where it is the dominant opacity source in the visual spectral region. This assumption…

We checked consistency between the copper abundance derived in six metal-poor stars using UV Cu II lines (which are assumed to form in LTE) and UV Cu I lines (treated in NLTE). Our program stars cover the atmosphere parameters which are…

Optical high-resolution spectra of V652 Her and HD 144941, the two extreme helium stars with exceptionally low C/He ratios, have been subjected to a non-LTE abundance analysis using the tools TLUSTY and SYNSPEC. Defining atmospheric…

We summarize recent results of quantitative spectral analyses using NLTE and metal line-blanketed LTE model atmospheres. Temperatures and gravities derived for hundreds of sdB stars are now available and allow us to investigate systematic…

We investigate departures from LTE in the line formation of Fe for a number of well-studied late-type stars in different evolutionary stages. A new model of Fe atom was constructed from the most up-to-date theoretical and experimental…

Quantitative analyses of low-mass hydrogen-deficient (super-)giant stars - so-called extreme helium stars - to date face two major difficulties. First, theory fails to reproduce the observed helium lines in their entirety, wings and line…

Manganese (Mn) is a key Fe-group elements, commonly employed in stellar population and nucleosynthesis studies to explore the role of SN Ia. We have developed a new non-local thermodynamic equilibrium (NLTE) model of Mn, including new…

Helium rich subdwarf O stars (sdOs) are hot compact stars in a pre-white dwarf evolutionary state. Most of them have effective temperatures and surface gravities in the range Teff = 40,000-50,000 K and log g = 5.5-6.0. Their atmospheres are…

HD76431 is a slow rotating post-HB star that shows an underabundance of helium by 0.5 dex relative to the solar value. These observational facts suggest that atomic diffusion could be active in its atmosphere. We have used the MMT and Bok…

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,…

We address the origin and evolutionary status of hot subdwarf stars by studying the optical spectral properties of 58 subdwarf O (sdO) stars. Combining them with the results of our previously studied subdwarf B (sdB) stars, we aim at…

Based on photometric and astrometric data it has been proposed that Albus 1 (also known as CPD-20 1123) might be a hot white dwarf similar to G191-B2B or, alternatively, a hot subdwarf. We obtained a series of optical spectra showing that…

Hot subdwarf B (sdB) and O (sdO) type stars are evolved helium-burning objects that lost their hydrogen envelope before the helium flash when their progenitors were close to the tip of the red giant branch. They populate the extreme…

Three members of the new class of pulsating sdB stars (sdBV or EC 14026 stars) are analysed from Keck HIRES spectra using line blanketed NLTE and LTE model atmospheres. Atmospheric parameters (Teff, log g, He/H), metal abundances and…

The non-local thermodynamic equilibrium (NLTE) line formation of neutral boron in the atmospheres of cool stars are investigated. Our results confirm that NLTE effects for the B I resonance lines, which are due to a combination of…

We developed a comprehensive model atom of Sc II-Sc III. Abundances of scandium for a sample of eight unevolved A9-B3 type stars with well-determined atmospheric parameters were determined based on the non-local thermodynamic equilibrium…

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…

We report on the analysis of high-resolution optical spectra for 77 subdwarf B (sdB) stars from the ESO Supernova Ia Progenitor Survey. Effective temperature, surface gravity, and photospheric helium abundance are determined simultaneously…