  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).
