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The coolest DA white dwarfs detected at soft X-ray wavelengthsNew soft X-ray/EUV photometric observations of the DA white dwarfs KPD 0631 + 1043 = WD 0631 + 107 and PG 1113 + 413 = WD 1113 + 413 are analyzed. Previously reported soft X-ray detections of three other DAs and the failure to detect a fourth DA in deep Exosat observations are investigated. New ground-based spectra are presented for all of the objects, with IUE Ly-alpha spectra for some. These data are used to constrain the effective temperatures and surface gravities. The improved estimates of these parameters are employed to refer a photospheric He abundance for the hotter objects and to elucidate an effective observational low-temperature threshold for the detection of pure hydrogen DA white dwarfs at soft X-ray wavelengths.
Document ID
19920065506
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Kidder, K. M.
(NASA Headquarters Washington, DC United States)
Holberg, J. B.
(Arizona, University Tucson, United States)
Barstow, M. A.
(NASA Headquarters Washington, DC United States)
Tweedy, R. W.
(Leicester, University United Kingdom)
Wesemael, F.
(Montreal, Universite Montreal, Canada)
Date Acquired
August 15, 2013
Publication Date
July 20, 1992
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 394
Issue: 1 Ju
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
92A48130
Funding Number(s)
CONTRACT_GRANT: NAG5-434
Distribution Limits
Public
Copyright
Other

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