\gamma Cas is an unusual classical Be star for which the optical-band and hard X-ray fluxes vary on a variety of timescales .
We report results of a nine-year monitoring effort on this star with a robotic ground-based ( APT ) telescope in the B , V filter system as well as simultaneous observations in 2004 November with this instrument and the Rossi X-ray Timing Explorer ( RXTE ) telescope .
Our observations disclosed no correlated optical response to the rapid X-ray flares in this star , nor did the star show any sustained flux changes any time during two monitored nights in either wavelength regime .
Optical light curves obtained in the APT program revealed , consistent with an earlier study by Robinson et al. , that \gamma Cas undergoes \sim 3 % -amplitude cycles with lengths of 60–90 days .
Our observations in 2004 showed a similar optical cycle .
Over the nine days we monitored the star with the RXTE , the X-ray flux varied in phase with its optical cycle and with an amplitude predicted from the data in Robinson et al .
In general , the amplitude of the V magnitude cycles are 30–40 % larger than the corresponding B amplitude , suggesting the seat of the cycles is circumstellar .
The cycle lengths constantly change and can damp or grow on timescales as short as 13 days .
We have also discovered a coherent period of 1.21581 { \pm 0.00002 } days in all our data , which is consistent only with rotation .
The full amplitude of this variation is 0.0060 in both filters , and surprisingly , its waveform is almost sawtooth in shape .
This variation probably originates on the star ’ s surface .
This circumstance hints at the existence of a strong magnetic field with a complex topology and an associated heterogeneous surface composition .