Rapid oscillations in cataclysmic variables. VIII - YY Draconis (=3A 1148 + 719)

A 16th magnitude cataclysmic variable presumably a dwarf nova, was detected near one of the positions permitted for the hard (2-10 keV) X-ray source 3A 1148 + 719. The optical and UV spectra of YY Dra are fairly typical of cataclysmic variables, except that the TiO absorption bands of an M dwarf can be seen for greater than 5000 A. This shows that the accretion disk is intrinsically faint in quiescence, suggesting a very low accretion rate. Yet the fairly blue continuum slope in the vacuum UV indicates the presence of a small hot object, presumably the white dwarf. The radial velocities at H-alpha indicate a 4.0-hr orbital period, and the IR light curve appears to show the expected 'double-humped' waveform from the distorted secondary. High-speed photometry in the U band reveals a stable periodicity of about 1-percent semiamplitude at a period of 275 s, with some power also in the subharmonic at about 550 s.