The activity cycle of V833 Tau from photometric data for 1899–2009

Photoelectric B -band data and calibrated photographic estimates are used to plot a combined light curve of the red dwarf V833 Tau (dK5e) covering 1899–2009. A frequency analysis was applied to the resulting series of yearly mean B magnitudes, yielding possible photospheric activity cycles acting on various timescales. The high-amplitude variations, up to 0.6 m (0.8), follow a cycle with a duration of 78.25 yrs. A 18.8-year cycle with an amplitude of 0.39 m –0.16 m was also detected, and changes of its characteristics for each observing epoch considered. The star becomes redder at epochs of decreased brightness, suggesting that the 18-year cycle is related to spot-formation processes. The existence of the shorter 6.4-year and 2.5-year cycles reported earlier is confirmed.