Photometric changes and spot motion in Lambda Andromedae

The V-band photometry presented for the long period RS CVn-type binary Lambda Andromedae covers one complete cycle in 1981-1982, and more than three continuous cycles in 1982-1983. An analysis of the existing epochs of maximum and minimum light confirms the photometric period given by Boyd et al. (1983), but discloses the presence of a quasi-periodic trend in the O-C curve that suggests cyclic changes on a time scale of about 9 years. The frequency spread around the fundamental periodicity revealed by Fourier analysis of the 1982-1983 record may be interpreted as due to the presence of dark spots, highly spread in latitude, which move at different velocities because of the star's differential rotation.