UNSPECIFIED (2004) Composite accretion disk and white dwarf photosphere analyses of the FUSE and Hubble Space Telescope observations of EY Cygni. ASTRONOMICAL JOURNAL, 128 (4). pp. 1795-1801. ISSN 0004-6256

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Abstract

We explore the origin of FUSE and Hubble Space Telescope STIS far-UV spectra of the dwarf nova EY Cygni during its quiescence using combined high-gravity photosphere and accretion disk models, as well as model accretion belts. The best-fitting single-temperature white dwarf model to the FUSE plus STIS spectrum of EY Cyg has T-eff = 24, 000 K and log g = 9.0 with an Si abundance of 0.1 times solar and C abundance of 0.2 times solar, but the distance is only 301 pc. The best-fitting composite model consists of a white dwarf with T-eff = 22, 000 K and log g = 9, plus an accretion belt with T-belt = 36, 000 K covering 27% of the white dwarf surface with V-belt sin i = 2000 km s(-1). The accretion belt contributes 63% of the far-UV light and the cooler white dwarf latitudes contribute 37%. This fit yields a distance of 351 pc, which is within 100 pc of our adopted distance of 450 pc. EY Cyg has very weak C IV emission and very strong N v emission, which is atypical of the majority of dwarf novae in quiescence. We also conducted a morphological study of the surroundings of EY Cyg using direct imaging in narrow nebular filters from ground-based telescopes. We report the possible detection of nebular material associated with EY Cyg. Possible origins of the apparently large N V/C IV emission ratio are discussed in the context of nova explosions, contamination of the secondary star, and accretion of nova abundance-enriched matter back to the white dwarf via the accretion disk or as a descendant of a precursor binary that survived thermal-timescale mass transfer. The scenario involving pollution of the secondary by past novae may be supported by the possible presence of a nova remnant - like nebula around EY Cyg.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Journal or Publication Title:	ASTRONOMICAL JOURNAL
Publisher:	UNIV CHICAGO PRESS
ISSN:	0004-6256
Date:	October 2004
Volume:	128
Number:	4
Number of Pages:	7
Page Range:	pp. 1795-1801
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/7972

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