White Dwarfs in Cataclysmic Variables: HST Results on GW LIB And Gleanings from SDSS Provide Insight on the Effects of Accretion

Abstract

Cataclysmic variables (CVs) provide a rich laboratory to study the effects of mass transfer and accretion on the properties and evolution of white dwarfs. One interesting aspect is the effect of accretion on the instability strip. So far, there is only one ZZ Cet pulsator known to be a CV - GW Lib. Our UV spectra obtained with HST provide interesting results. The UV light curve of GW Lib reveals large amplitude pulsations at 3 periods while the spectrum shows a temperature hotter than single DAVs. However, our UV data on systems with WD temperatures in the DAV zone show no pulsation. The emerging SDSS database provides a rich resource for studies of many other aspects of accretion. So far, there are more than 60 new CVs and more than 100 WD+M pairs that have been found. A few of the unusual systems and some of the results on the pairs are highlighted. The SDSS Web site is SDSS.