Rapid oscillations in cataclysmic variables. I. The 71 second oscillation of DQ Herculis.

A photometric study of the 71-sec oscillation in the old nova DQ Her is presented. It is found that all timings of the oscillation maxima can be phased with a simple ephemeris, that the oscillation exhibits many details in its phase and amplitude variations around the binary orbit, and that the previously discovered oscillation phase shift in eclipse is indeed present. The multicolor observations indicate that the visible oscillation arises from reprocessing of the white dwarf's pulsed UV flux by the accretion disk. Eclipse timings are reported which show that a sinusoidal modulation with a period of about 14 yr is present in all timings since 1954. It is noted that this effect cannot be easily ascribed to either a distant companion or classical apsidal motion.