Photometric study of the active Algol system RZ Cassiopeiae

Abstract

The active Algol binary system RZ Cas is studied photometrically. UBV light curves are analyzed with a light-curve synthesis method. The analysis yields a semidetached configuration, in which the more massive detached primary is eclipsed by the contact companion at the primary eclipse, i.e., RZ Cas is a usual semidetached Algol-type system. The photometric elements deduced indicate that the primary minimum is due to partial occultation, despite frequent occurrences of flat bottom in the primary minimum. Combined with the published spectroscopic data, the system parameters are derived. Photoelectric monitoring of the primary minimum reveals changes in the shape of the primary minimum as well as changes in the orbital period, suggesting activities of the system. Some proposed models to explain activities of the active Algols are discussed. The reason why the flat bottom appears so frequently at the middle of the primary minimum remains unclear.