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A Hubble Space Telescope study of the underlying white dwarf in the dwarf nova VW Hydri during quiescenceWe have analyzed a far-ultraviolet spectrum of the dwarf nova VW Hyi obtained during quiescence with the Hubble Space Telescope Faint Object Spectrograph (HST FOS). The observation occurred 10 days after the return to optical quiescence from a superoutburst of VW Hyi. The spectrum reveals a very strong Stark-broadened Ly-alpha absorption with narrow geocoronal emission, and a very rich metallic absorption-line spectrum dominated by strong resonance absorption features of singly and doubly ionized silicon and carbon, the first solid identification of metallic absorption features arising in the accreted atmosphere of the white dwarf. We confirm the reported low-resolution IUE detection of the underlying white dwarf photosphere by Mateo & Szkody. A synthetic spectral analysis with hot, high-gravity LTE model atmospheres yields a best-fit model with the following parameters: T(sub eff) = 22,000 +/- 1000 K, log g = 8.0 +/- 0.3, with chemical abundances for oxygen of 0.3 times solar, for nitrogen of 5 times solar, and for all other heavy elements of 0.15 times solar. Based upon our absorption-line measurements of the observations at different orbital phases, we find no conclusive evidence of equivalent width variations with orbital phase. In the absence of any significant reduction of the white dwarf's core mass by past nova explosions, its lower limit cooling age is approximately 50 million years.
Document ID
19950054421
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Sion, Edward M.
(Villanova University Villanova, PA, United States)
Szkody, Paula
(University of Washington, Seattle, WA United States)
Cheng, Fu-Hua
(University of Maryland, College Park, MD United States)
Huang, Min
(Villanova University Villanova, PA, United States)
Date Acquired
August 16, 2013
Publication Date
May 10, 1995
Publication Information
Publication: Astrophysical Journal, Part 2 - Letters
Volume: 444
Issue: 2
ISSN: 0004-637X
Subject Category
Astronomy
Accession Number
95A86020
Funding Number(s)
CONTRACT_GRANT: NAG5-2374
CONTRACT_GRANT: NAG5-2429
CONTRACT_GRANT: NAS5-26555
CONTRACT_GRANT: NAGW-3158
Distribution Limits
Public
Copyright
Other

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