A soft X-ray survey of hot white dwarfs with Exosat
Broadband multicolor soft X-ray photometry of 34 hot white dwarfs is presented, obtained with the Low Energy Imaging Telescopes on Exosat. By combining the soft X-ray fluxes with measurements of the stellar parameters in the UV and optical bands, photospheric He abundances for 16 of the 21 hot DA white dwarfs are derived. Supplemented by five stars previously observed with Einstein, a total of 21 helium abundances is compiled which span a range between He/H less than 10 to the minus 5 and He/H = 1/100, for effective temperatures (Te) between 25,000 and 65,000 K. For the cooler DAs in the sample (Te less than 45,000 K) evidence is found that accretion from the interstellar medium is the dominant mechanism determining the photospheric He content. For the six stars at higher Te, no compelling evidence for a positive correlation between Te and He/H is found. 43 refs.
- Research Organization:
- SRON, Laboratorium voor Ruimteonderzoek, Utrecht (Netherlands)
- OSTI ID:
- 5856576
- Journal Information:
- Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 339; ISSN ASJOA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
ASTRONOMY
CHEMICAL COMPOSITION
DWARF STARS
ELECTROMAGNETIC RADIATION
ELEMENTS
FLUIDS
GASES
HELIUM
INTERSTELLAR SPACE
IONIZING RADIATIONS
NONMETALS
PHOTOMETRY
RADIATION FLUX
RADIATIONS
RARE GASES
SATELLITES
SOFT X RADIATION
SPACE
STAR ACCRETION
STAR EVOLUTION
STARS
WHITE DWARF STARS
X RADIATION