The Constitution of the Atmospheric Layers and the Extreme Ultraviolet Spectrum of Hot Hydrogen-rich White Dwarfs
Abstract
An analysis is presented of the atmospheric properties of hot, H-rich, DA white dwarfs that is based on optical, UV, and X-ray observations aimed at predicting detailed spectral properties of these stars in the range 80-800 A. The divergences between observations from a sample of 15 hot DA white dwarfs emitting in the EUV/soft X-ray range and pure H synthetic spectra calculated from a grid of model atmospheres characterized by Teff and g are examined. Seven out of 15 DA stars are found to consistently exhibit pure hydrogen atmospheres, the remaining seven stars showing inconsistency between FUV and EUV/soft X-ray data that can be explained by the presence of trace EUV/soft X-ray absorbers. Synthetic data are computed assuming two other possible chemical structures: photospheric traces of radiatively levitated heavy elements and a stratified hydrogen/helium distribution. Predictions about forthcoming medium-resolution observations of the EUV spectrum of selected hot H-rich white dwarfs are made.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1992
- DOI:
- 10.1086/171310
- Bibcode:
- 1992ApJ...390..590V
- Keywords:
-
- Extreme Ultraviolet Radiation;
- Hot Stars;
- Stellar Atmospheres;
- Stellar Spectra;
- White Dwarf Stars;
- X Ray Stars;
- Atmospheric Stratification;
- Ultraviolet Astronomy;
- Ultraviolet Spectra;
- X Ray Astronomy;
- X Ray Spectra;
- Astrophysics;
- STARS: ATMOSPHERES;
- ULTRAVIOLET: STARS;
- STARS: WHITE DWARFS;
- X-RAYS: STARS