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We present the latest Hubble Space Telescope Space Telescope Imaging Spectrograph (HST STIS) E140M farultraviolet (FUV) spectrum of the dwarf nova WZ Sge, obtained in 2004 July, 3 yr following the early superoutburst of 2001 July. With a temperature T % 15;000 K, the white dwarf (WD) is still $1500 K above its quiescent temperature, it has a FUV flux level almost twice its preoutburst value, and its spectrum does not distinctly exhibit the quasi-molecular hydrogen feature around 1400 8, which was present in the International Ultraviolet Explorer (IUE ) and HST Goddard High Resolution Spectrograph (GHRS) preoutburst data. This is a clear indication that even 3 yr after outburst, the system is still showing the effect of the outburst. We model the cooling curve of WZ Sge, over a period of 3 yr, using a stellar evolution code including accretion and the effects of compressional heating. Assuming that compressional heating alone is the source of the energy released during the cooling phase, we find that (1) the mass of the WD must be quite large (%1:0 AE 0:2 M ), and (2) the mass accretion rate must have a time-averaged (over 52 days of outburst) value of order 10 À8 M yr À1 or above. The outburst mass accretion rate derived from these compressional heating models is larger than the rates estimated from optical observations (Patterson et al.) and from a FUV spectral fit (Long et al.) by up to 1 order of magnitude. This implies that during the cooling phase the energy released by the WD is not due to compressional heating alone. We suggest ongoing accretion during quiescence as an additional source of energy.

We present a 904-1183 8 spectrum of the dwarf nova VW Hyi taken with the Far Ultraviolet Spectroscopic Explorer during quiescence, 11 days after a normal outburst, when the underlying white dwarf accreter is clearly exposed in the far-ultraviolet. However, model fitting shows that a uniform-temperature white dwarf does not reproduce the overall spectrum, especially at the shortest wavelengths. A better approximation to the spectrum is obtained with a model consisting of a white dwarf and a rapidly rotating ''accretion belt.'' The white dwarf component accounts for 83% of the total flux, has a temperature of 23,000 K, a v sin i ¼ 400 km s À1 , and a low carbon abundance. The best-fit accretion belt component accounts for 17% of the total flux, with a temperature of about 48,000-50,000 K and a rotation rate V rot sin i around 3000-4000 km s À1 . The requirement of two components in the modeling of the spectrum of VW Hyi in quiescence helps to resolve some of the differences in interpretation of ultraviolet spectra of VW Hyi in quiescence. However, the physical existence of a second component (and its exact nature) in VW Hyi itself is still relatively uncertain, given the lack of better models for spectra of the inner disk in a quiescent dwarf nova.