THE X-RAY SOURCE IN NONMAGNETIC CATACLYSMIC VARIABLES

We have analysed all available ROSAT PSPC observations of non-magnetic cataclysmic variables. The VY Sd and non-SU UMa systems have harder X -ray spectra than the SU UMa and UX UMa systems. The old nova RR Pic h as a very soft X-ray spectrum and might not be an ordinary non-magneti c cataclysmic variable. There appears to be no clear correlation of th e X-ray temperature, the emission measure, or the X-ray luminosity wit h the accretion rate. However, we have found an anti-correlation betwe en the observable emission measure and the orbital inclination of the system, from which we conclude that the X-ray emitting region is close to the white dwarf and has a size smaller than the white dwarf radius .