ITAL]ROSAT[/ITAL] High Resolution Imager Observations of Three Magnetic Cataclysmic Variables: EP Draconis, EUVE J2115−58, and AR Ursae Majoris

Abstract

I present ROSAT HRI observations of the magnetic cataclysmic variables EP Dra, EUVE J2115-58, and AR UMa. The HRI light curve for EP Dra shows the typical polar behavior for one-pole accretion. When the data from a 1993 PSPC observation are phased correctly, the PSPC and HRI light curves appear nearly identical in behavior. The eclipses differ in width, however. The PSPC eclipse is about half the width of the HRI eclipse, suggesting that the HRI eclipse is a combined eclipse and stream occultation. The EUVE J2115-58 observation was obtained in two parts approximately 180 days apart. The count rates differ by a factor of 3 between the two epochs. The X-ray data do not resolve the period ambiguity, because the light curves look very similar when folded on every published period. A period search using the longer observation yields two periods of 102.6 and 110.4 minutes. The HRI observation for AR UMa occurred during an off state. AR UMa is detected at a significance level of 3 σ at a luminosity of ~4 × 1029 ergs s-1, which likely arises from the M dwarf companion.