RX J1039.7-0507: A New Intermediate Polar and Probable Recent Nova, possessing a large Reflection Effect

The ROSAT source RX J1039.7-0507, known from its optical spectrum to be a Cataclysmic Variable star, is shown from high speed photometry to have an orbital period of 1.574 h. The system has a nearly sinusoidal photometric modulation with a range of 1.1 mag which we interpret as the reflection effect caused by a very hot white dwarf primary. This suggests that a nova explosion occured on the primary in the relatively recent past. In addition, RX J1039.7-0507 has periodic signals at 1932.5 s and 721.9 s which, with the aid of other periods present at low amplitude, we interpret as an orbital sideband and the first harmonic of the primary's spin period. RX J1039.7-0507 is therefore an intermediate polar with a spin period of 1444 s (24.07 min).