The cooling of the white dwarf in OY Car after 1992 superoutburst

Abstract

HST observations of the eclipsing dwarf nova OY Car after its 1992 April superoutburst are used to isolate ultraviolet spectra (1150–2500 A at 9.2 A FWHM resolution) of the white dwarf, the accretion disk, and the bright spot. The white dwarf spectra have a Stark‐broadened photospheric Lα absorption, but are veiled by a forest of blended Fe II features that we attribute to absorption by intervening disk material. Spectral fits give white dwarf temperatures changing from ∼19500 K just after outburst ∼17400 K around three months after outburst. The temperature of intervening disk material is ∼8600 K–9800 K; the velocity dispersion of the intervening disk material is ∼60–70 km/s. Fitting results also shows that the decay time of white dwarf temperature is ∼27 days, that is much shorter than ∼687 days in dwarf nova WZ Sge.