相关论文: EC 11481-2303 - A Peculiar Subdwarf OB Star Revisi…

Spectral analyses of extreme horizontal branch (EHB) stars indicate a trend to supersolar heavy-metal abundances that is increasing with effective temperature. The sdOB EC11481-2303 is such a star, located at the very hot end of the EHB. In…

We have detected three new hydrogen-deficient (H < 0.001 mass fraction) pre-white dwarfs (WDs) with helium-dominated atmospheres. The first object is a relatively cool PG1159 star (effective temperature Teff = 72,000 K) that has the lowest…

Helium-rich subdwarf B (He-sdB) stars represent a small group of low-mass hot stars with luminosities greater than those of conventional subdwarf B stars, and effective temperatures lower than those of subdwarf O stars. By measuring their…

Subdwarf B (sdB) stars are core helium-burning stars with stratified atmospheres. Their atmospheres are dominated by hydrogen (H) while the helium (He) and metal abundances are shaped by an interplay of gravitational settling and radiative…

Helium-burning hot subdwarf stars of spectral types O and B (sdO/B) are thought to be produced through various types of binary interaction. The helium-rich hot subdwarf star EC22536-5304 was recently found to be extremely enriched in lead.…

We derive the stellar parameters of a sample of Galactic early-O type stars by analysing their UV and Far-UV spectra from FUSE (905-1187A), IUE, HST-STIS and ORFEUS (1200-2000A). The data have been modeled with spherical, hydrodynamic,…

Hot, compact, hydrogen-deficient pre-white dwarfs (pre-WDs) with effective temperatures of Teff > 70,000 K and a surface gravity of 5.0 < log g < 7.0 are rather rare objects despite recent and ongoing surveys. It is believed that they are…

We present high-resolution VLT spectra of a new helium-rich DO white dwarf and a new PG1159 star, which we identified in the ESO SPY survey. We performed NLTE model atmosphere analyses and found that the PG1159 star is a low-gravity,…

We present a detailed analysis of the UV spectrum of the calibration star Bd+28 4211 using high-quality spectra obtained with the HST and FUSE satellites. To this aim, we compare quantitatively the observed data with model spectra obtained…

We present a comprehensive multiwavelength analysis of the hot DB white dwarf PG 0112+104. Our analysis relies on newly-acquired FUSE observations, on medium-resolution FOS and GHRS data, on archival high-resolution GHRS observations, on…

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…

We present a LTE model atmosphere analysis of the medium and long wavelength spectrum of the cool DO white dwarf HD149499B. This observation in the spectral range 230-700 A supplements a previous analysis of an ORFEUS spectrum between 912…

We present high-resolution VLT spectra of a new DO white dwarf and a new PG1159 star, which we identified in the ESO SPY survey. The PG1159 star is a low-gravity, extremely hot (Teff=160,000 K, log g=6) star, having a C/He dominated…

We studied the class of DB white dwarf stars, using re-calibrated UV spectra for thirty four DBs obtained with the IUE satellite. By comparing the observed energy distributions with model atmospheres, we simultaneously determine…

We present the second part of our detailed analysis of the hot sdO and spectroscopic standard star BD+28 4211, in which we focus on the optical spectrum. In the first part of our study, we determined the abundances of some 11 metals…

We have performed a non-LTE spectroscopic analysis using far-UV and UV data of the central star of the planetary nebula K1-26 (Longmore 1), and found Teff = 120+/-10 kK, logg = 6.7 +0.3/-0.7, and y = 0.10. The temperature is significantly…

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…

We present a comprehensive study of Far Ultraviolet Spectroscopic Explorer (FUSE) spectra (912-1190 A) of two members of the PG1159 spectral class, which consists of hydrogen-deficient (pre-) white dwarfs with effective temperatures in the…

We present the first time abundance analysis of a very metal-poor carbon-enhanced star CD-27 14351 based on a high resolution (R ~ 48000) FEROS spectrum. Our abundance analysis performed using Local Thermodynamic Equilibrium (LTE) model…

For the precise spectral analysis of hot stars, advanced stellar-atmosphere models that consider deviations from the local thermodynamic equilibrium are mandatory. This requires accurate atomic data to calculate all transition rates and…