SUZAKUOBSERVATIONS OF THE DWARF NOVA V893 SCORPII: THE DISCOVERY OF A PARTIAL X-RAY ECLIPSE

Abstract

V893 Sco is an eclipsing dwarf nova that had attracted little attention from X-ray astronomers until it was proposed as the identification of an Rossi X-Ray Timing Explorer all-sky slew survey (XSS) source. Here, we report on the pointed X-ray observations of this object using Suzaku. V893 Sco was in quiescence at the time, as indicated by the coordinated optical photometry we obtained at the South African Astronomical Observatory. Our Suzaku data show V893 Sco to be X-ray bright, with a highly absorbed spectrum. Most importantly, we have discovered a partial X-ray eclipse in V893 Sco. This is the first time that a partial eclipse is seen in X-ray light curves of a dwarf nova. Our preliminary simulations demonstrate that the partial X-ray eclipse can be in principle reproduced if the white dwarf in V893 Sco is partially eclipsed. Higher quality observations of this object have the potential to place significant constraints on the latitudinal extent of the X-ray emission region and thereby discriminating between an equatorial boundary layer and a spherical corona. The partial X-ray eclipse therefore makes V893 Sco a key object in understanding the physics of accretion in quiescent dwarf nova.