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Paper: An Intensive Study of the Dwarf Nova System VW Hydri
Volume: 372, 15th European Workshop on White Dwarfs
Page: 505
Authors: Long, K.S.; Froning, C.S.; Gaensicke, B.T.; Knigge, C.
Abstract: The FUV spectra of quiescent dwarf novae are complex, and evolve with time from outburst. Although in many cases, the white dwarf (WD) dominates in quiescence, various systems also show possible contributions from a rapidly rotating accretion belt, from a boundary layer, and from the accretion disk. It has, however, been extremely difficult to distinguish them from one another, in part because there have been very few campaigns dedicated to a single system responding to a single outburst. Here we describe, the results of a sequence of 13 FUSE observations of VW Hyi that extend over a period of 30 days from the late decline phase of a super-outburst that occurred in August 2004 through the following normal outburst. Spectra obtained during epochs 2 through 10 and 12 and 13 are dominated by the WD, which evolves from an effective temperature about 24,500 K to one that is about 19,600 K. The observations close to the super-outburst and just after the normal outburst have an additional component that can be characterized as a flat, relatively featureless continuum. The amplitude of the continuum declines with time but the shape is fairly constant. The absence of higher order Lyman lines in the spectrum of the second component indicates that it does not arise from the WD surface. The second component complicates analyzes of surface abundances on the WD photosphere. We will discuss our attempts to model the spectra and to explain the origin of the second component.
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