Contact Binary Variables as X-ray Sources

Abstract

We present cross-identification of archived X-ray point sources with W UMa variable stars found in the All-Sky Automated Survey (ASAS). In a surveyed sky area of 300 square degrees of ASAS, 36 W UMa stars have been found associated with X-ray emission. We compute the distances of these W UMa systems and hence their X-ray luminosities. Our data support the "supersaturation" phenomenon seen in these fast rotators, namely that the faster a W UMa star rotates, the weaker its X-ray luminosity.