Rotational and Cyclical Variability in γ Cassiopeia

We report results of a nine-year monitoring effort on the unusual classicalBe with a robotic ground-based (APT) B,V-filtered telescope as well assimultaneous observations in 2004 November with this instrument and the RXTE(X-ray) telescope. Our observations disclosed no correlated optical response tothe rapid X-ray flares in this star, nor did the star show any sustained fluxchanges during the course of either of the two monitored nights in eitherwavelength regime. Our optical light curves reveal that gamma Cas undergoes\~3%-amplitude cycles with lengths of 60--90 days. Over the nine days wemonitored the star with the RXTE, the X-ray flux varied in phase with itsoptical cycle and with an amplitude predicted from correlated optical/X-raydata from an earlier paper. The amplitudes of the V magnitude cycles are30--40% larger than the B amplitudes, suggesting the seat of the cycles iscircumstellar. The cycle lengths constantly change and can damp or grow ontimescales as short as 13 days. We have also discovered a coherent period of1.21581 +/-0.00002 days in all our data, which is consistent only withrotation. The full amplitude of this variation is 0.0060 in both filters. Thederived waveform, somewhat surprisingly, is almost sawtooth in shape. Thisvariation probably originates on the star's surface. This circumstance hints atthe existence of a strong magnetic field with a complex topology and anassociated heterogeneous surface composition.Comment: 31 pages, 7 figures. Submitted to The Astrophysical Journa