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

Early Herbig Be (HBe) stars are massive, young stars accreting through the Boundary Layer mechanism. However, given the rapid ($<$ 2 Myr) evolution of early Herbig stars to the main-sequence phase, studying the evolution of the…

We present results of our calculations of NLTE model stellar atmospheres for hot Population III stars composed of hydrogen and helium. We use our own computer code for calculation of spherically symmetric NLTE model atmospheres in…

182 single-lined hot subdwarf stars are identified by using spectra from the sixth and seventh data release (DR6 and DR7) of the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) survey. We classified all the hot subdwarf…

PG1159 stars are hot, hydrogen-deficient (pre-) white dwarfs with atmospheres mainly composed of helium, carbon, and oxygen. The unusual surface chemistry is the result of a late helium-shell flash. Observed element abundances enable us to…

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 carried out a quantitative spectral analysis of 73 hot subluminous O-stars selected from the SDSS spectral database. While the helium deficient sdOs are scattered over a wide range of effective temperature and gravity, the helium…

Photometric surveys at optical, ultraviolet, and infrared wavelengths provide ever growing datasets as major surveys proceed. Colour-colour diagrams are useful tools to identify classes of stars and to provide large samples. Combining all…

We determine Mg abundances in 6 Gaia benchmark stars using theoretical one-dimensional (1D) hydrostatic model atmospheres, as well as temporally- and spatially-averaged 3D model atmospheres (<3D>). The stars cover a range of Teff from 4700…

Hot subdwarf stars of types O and B represent a poorly understood phase in the evolution of low-mass stars. Many subdwarfs show rich oscillations and are among the most chemically peculiar stars known. Two intermediate He-rich hot subdwarf…

Un-evolved, very metal-poor stars are the most important tracers of the cosmic abundance of lithium in the early universe. Combining the standard Big Bang nucleosynthesis model with Galactic production through cosmic ray spallation, these…

We present NLTE abundances and atmospheric parameters for three metal-poor stars ([Fe/H]<-2) in Coma Berenices ultra-faint dwarf galaxy (UFD). The derived results are based on new photometric observations obtained with the 2.5-m telescope…

Different simplified approaches are used to account for the non-local thermodynamic equilibrium (NLTE) effects with 3D hydrodynamical model atmospheres. In certain cases, chemical abundances are derived in 1D NLTE and corrected for the 3D…

Aims. The statistical equilibrium of neutral and ionized silicon in the atmospheres of metal-poor stars is discussed. Non-local thermodynamic equilibrium effects are investigated and the silicon abundances in metal-poor stars determined.…

LS V +4621 is the DAO-type central star of the planetary nebula Sh 2-216. We perform a comprehensive spectral analysis of high-resolution, high-S/N ultraviolet observations obtained with FUSE and STIS aboard the HST as well as the optical…

Hot subdwarf B stars (sdBs) are evolved core helium-burning stars with very thin hydrogen envelopes. In order to form an sdB, the progenitor has to lose almost all of its hydrogen envelope right at the tip of the red giant branch. In close…

Optical observations from 1989 of the SMC B[e] supergiant star S23 revealed the presence of photospheric HeI absorption lines. In our high-resolution optical spectra from 2000, however, we could not identify any HeI line. The observed…

Hot subdwarf (SD) stars are the stripped cores of red giant stars in transition to the white dwarf sequence. The B-type subdwarfs (sdB) are powered by helium fusion in the core, more evolved ones (sdO) by shell burning. Low mass SDs may…

Aims. This study aims to determine the level and constancy of the Spite plateau as definitively as possible from homogeneous high-quality VLT-UVES spectra of 19 of the most metal-poor dwarf stars known. Methods. Our high-resolution (R ~…

We present a detailed analysis of 26 barium stars, including dwarf barium stars, providing their atmospheric parameters (Teff, log g, [Fe/H], vt) and elemental abundances. We aim at deriving gravities and luminosity classes of the sample…

Neutral sodium is an important tracer of the Galactic chemical evolution, a powerful diagnostic of different stellar populations, and the subject of detailed studies of exoplanet atmospheres via transmission spectroscopy. This work aims to…