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Discovery of a new white dwarf in a binary system (EUVE 0720-317) in the Extreme Ultraviolet Explorer survey and implications for the late stages of stellar evolutionA new precataclysmic binary is identified in the Extreme Ultraviolet Explorer (EUVE) all-sky survey. The bright source EUVE 0720-317 shows a hot hydrogen-rich white dwarf optical continuum with overlying narrow Balmer-line emission. Using high signal-to-noise ratio spectroscopy in the 4100-6700 A range, we identify a late-type companion and find a 1.3d periodic modulation in the emission-line velocities and strengths. This is the signature of Feige 24-type close binary systems. We determine the components' spectral types (DAO and dM0-2), orbital velocities (K(sub DAO) = 104 +/- 12 km/s, K(sub dM) = 96 +/- 7 km/s), and systemic velocity (gamma = 15 +/- 12 km/s). A first estimate of the white dwarf gravitational redshift, gamma(sub g) = 45 +/- 20 km/s, and theoretical mass-radius relationships imply R(sub DAO) = 0.010-0.016 solar radius and M(sub DAO) = 0.55-0.90 solar mass. The orbital inclination is therefore i greater than or equal to 52 deg, consistent with the large amplitude variations found in H-alpha equivalent widths that imply i greater than or equal to 42 deg. We show that the discovery of new close WD + MS binary systems in extreme ultraviolet (EUV) sky surveys has important implications for theory of common-envelope evolution, in particular for the predicted close binary birthrate and orbital and stellar parameters.
Document ID
19950038137
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Vennes, Stephane
(University of California, Berkeley, CA United States)
Thorstensen, John R.
(Dartmouth College, Hanover, NH United States)
Date Acquired
August 16, 2013
Publication Date
September 20, 1994
Publication Information
Publication: Astrophysical Journal, Part 2 - Letters
Volume: 433
Issue: 1
ISSN: 0004-637X
Subject Category
Astronomy
Accession Number
95A69736
Funding Number(s)
CONTRACT_GRANT: NAS5-30180
CONTRACT_GRANT: NAG5-2405
Distribution Limits
Public
Copyright
Other

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