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Hubble Space Telescope high resolution spectroscoy of the exposed white dwarf in the dwarf nova VW Hydri in quiescence: A rapidly rotating white dwarfWe obtained a far-ultraviolet spectrum of the dwarf nova VW Hyi in quiescence, with the Hubble Space Telescope Goddard High Resolution Spectrograph covering the region of the Si iv lambda(lambda)1393, 1402 resonance doublet. The broad, shallow Si iv doublet feature is fully resolved, has a total equivalent width of 2.8 A, and is the first metal absorption feature to be clearly detected in the exposed white dwarf. Our synthetic spectral analysis, using a model grid constructed with the code TLUSTY, resulted in a reasonable fit to a white dwarf photosphere with T(sub eff) = 22,000 +/- 2000 K, log g = 8.0 +/- 0.3, an approximately solar Si/H abundance, and a rotational velocity, v sin i approximately equal to 600 km/s. This rotation rate, while not definitive because it is based upon just one line transition, is 20% of the Keplerian (breakup) velocity of the white dwarf and hence does not account for the unexpectedly low boundary-layer luminosity inferred from the soft-X-ray/extreme ultra-violet bands where most of the boundary-layer luminosity should be radiated. The predicted boundary-layer luminosity for a 0.6 solar mass white dwarf accreting at the rate 10(exp -10) solar mass/yr and rotating at 600 km/s, corresponding to VW Hyi in quiescence, is 2 x 10(exp 32) ergs/s when proper account is taken of the rotational kinetic energy going into spinning up the white dwarf. If the boundary-layer area is equal to that of the white dwarf, then T(sub bl) = 24,000 K. This is essentially identical to the photspheric luminosity and temperature determined in far-ultraviolet photospheric analyses. If the boundary-layer area is 10(exp -3) of the white dwarf surface area, then T(sub bl) = 136,000 K.
Document ID
19950056278
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Sion, Edward M.
(Villanova University Villanova, Pennsylvania, United States)
Huang, Min
(Villanova University Villanova, Pennsylvania, United States)
Szkody, Paula
(University of Washington, Seattle, Washington United States)
Cheng, Fu-Hua
(University of Maryland, College Park, College Park, Maryland United States)
Date Acquired
August 16, 2013
Publication Date
May 20, 1995
Publication Information
Publication: Astrophysical Journal, Part 2 - Letters
Volume: 445
Issue: 1
ISSN: 0004-637X
Subject Category
Astronomy
Accession Number
95A87877
Funding Number(s)
CONTRACT_GRANT: NAGW-3726
CONTRACT_GRANT: NAGW-3158
CONTRACT_GRANT: NAS5-26555
Distribution Limits
Public
Copyright
Other

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