Most active Algol-type system U Cephei: Drastic variations in the light curves obtained with the Transiting Exoplanet Survey Satellite

Abstract The most active Algol-type binary system, U Cephei, is well known for photometric disturbances. The large, rapid changes occurring in the light curves of out of the primary eclipse have been attributed to a cool spot on the primary star. We have studied the continuous light curves obtained with the Transiting Exoplanet Survey Satellite (TESS) and have found drastic disturbances, including many non-periodic “humps” and “dips” of various sizes. These cannot be explained by cool spots but rather by complex circumstellar matter (and related regions). By examining continuous data, we correlated light anomalies with circumstellar structures.