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Hot DA white dwarfs seen with Einstein, an ultrahot H- and He-poor white dwarf, and Zanstra temperatures of planetary nebula nucleiEinstein observations of hot DA white dwarfs are analyzed using model atmospheres. It is found that, for a relatively limited sample of stars, that hot He-poor stars like HZ 43 are indeed the exception, and that there is an apparent correlation between He/H ratio and increasing temperature. The seventh brightest soft X-ray source in the HEAO-A1 catalog, H1504+65, turns out to be an ultrahot white dwarf star, with a temperature of approximately 160,000 K, showing spectral features of the Zanstra method for determining the temperatures of central stars of planetary nebulae demonstrates that the H I Zanstra temperatures are indeed reliable and suggests that a substantial fraction of these central stars have He/H ratios which are considerably less than the solar value.
Document ID
19870055611
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Shipman, Harry L.
(Delaware, University Newark, United States)
Date Acquired
August 13, 2013
Publication Date
January 1, 1987
Publication Information
Publication: Societa Astronomica Italiana, Memorie
Volume: 58
Issue: 1 19
ISSN: 0037-8720
Subject Category
Astrophysics
Accession Number
87A42885
Funding Number(s)
CONTRACT_GRANT: NAG8-564
CONTRACT_GRANT: NAG5-348
CONTRACT_GRANT: NSF AST-85-15747
Distribution Limits
Public
Copyright
Other

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