Rapid Light Variations in Symbiotic Binary Stars

We describe a search for short time scale light variations in eight symbiotic binary stars. Five systems -- Z And, T CrB, AG Dra, BX Mon, and AX Per -- do not vary significantly on minute time scales during any of our observations. Three other symbiotics-CH Cyg, RS Oph, and MWC 56(#vary with amplitudes of Δ&U≥0.2 mag and ΔB≈0.2-0.3 mag on time scales of minutes to tens of minutes. Our data confirm semicoherent variations with P≈22 min in MWC 560. Similar variations with P≈82 min are present in RS Oph. Our data are not extensive enough to test conclusively for periodic light changes in CH Cyg. Rapid photometric variations in symbiotic stars have features in common with those observed in cataclysmic binaries. In particular, three symbiotic stars with rapid periodic light variations have amplitudes and spin periods similar to those observed in the DQ Her subclass of cataclysmic binaries. These systems appear to follow the same spin period-B amplitude relation as the DQ Her stars, which suggests that some symbiotic stars contain magnetic white dwarf secondaries. We also find a marginal correlation of flickering with luminosity; low luminosity hot components have a higher probability of flickering than high luminosity systems. Confirmation of both correlations require larger sample sizes.