We report over 5700 days (15 years) of VRI photometry of the yellow hypergiant variable star ρ Cassiopeiae. The V−I color curve is generally in phase with the V light curve on timescales of a few hundred days, but there is a 4000 day variation in V−I which is absent from the light curve. The approximate ratio of Δ(V−I)/ΔV is 0.46. The most conspicuous period in the light curve, in the autocorrelation diagram, and in the power spectrum is about 820 days. Less significant periods of 380, 510, and 645 days also appear in the power spectrum, and there are many subcycles in the light curve with lengths of 200–500 days. Since the most recent comprehensive analysis of the light curve of ρ Cas found a dominant period of 300 days, we conclude that the behavior of the star is quite variable with time.
John R. Percy et al 2000 PASP 112 363