Cataclysmic variables in the ROSAT PSPC All Sky Survey.

Abstract

91 cataclysmic variables from a sample of 162 systems with known or suspected binary periods were detected during the ROSAT XRT-PSPC All Sky Survey. Among the non-magnetic systems, the X-ray to optical/ultraviolet flux ratio decreases along the sequence SU UMa type - U Gem type - Z Cam type - UX UMa type, due mainly to variations in the optical/ultraviolet flux. 8 of the 10 brightest systems in terms of total PSPC countrate are magnetic systems. The 0.5-2.5keV X-ray luminosities range up to ~10^32^erg/s, the highest luminosities being those of four faraway DQ Her type systems. The other types of cataclysmic variables all have similar 0.5-2.5keV luminosity distributions. In an Appendix we compare the X-ray properties of cataclysmic variables with those of the dim X-ray sources in globular clusters.