1997PASP..109.1093R

begin{tex}Rapid time-resolution, Str{�o}mgren u-band photometry of CH∼cygni shows a marked decrease in quasi-periodic, short time scale (∼2000–3000 s) variability between 1995 August and 1996 June. In 1995, we detected variability of ∼0.3–0.4 mag with periods of ~2200 s and ~2700 s, which are remarkably similar to periods reported by Hoard (1993) from similar u-band measurements of CH∼Cyg in 1992. In contrast, during a number of nights in 1996 the u magnitude was roughly constant within 0.1 mag, and the light curves showed no evidence of rapid variability. The average u magnitude of CH∼Cyg decreased by ∼0.9 mag between 1995 and 1996, suggesting a common source for the quasi-periodic variability and the u-band luminosity, namely the hot component in the interacting binary. We discuss several possible explanations for this variability, including the spin of an accreting, magnetic white dwarf (as in the intermediate polar class of cataclysmic variables) and the reprocessing of accretion-induced radiation from the white dwarf in circumstellar material.