1988-1991 photometry of the chromospherically active double-lined binary system HD 163621 = V835 Herculis

Photometry in V and B with a 16-inch automatic telescope from 1988 to 1991 confirms the synchronous rotation suspected earlier and reveals variability up to 0.1M in the B bandpass at one epoch. Five spots formed with lifetimes ranging from 0.15 to 0.77 years. As with other rapid rotators, the differential rotation coefficient (k = 0.03) is significantly smaller than that of the Sun (k = 0.19).