CAOSP abstracts, Volume: 30, No.: 2, year: 2000

Abstract: New photoelectric U,B and V observations of the eclipsing contact system VW Cep were taken in 1998-2000 and 23 new minima times were determined. The (O-C) diagram constructed using photographic and photoelectric minima times can be explained by the light-time effect caused by the presence of a third and fourth body in the system and the long-term period decrease interpreted by the mass transfer from the more to the less massive component or/and the magnetic-braking process. The sudden period increase detected in 1999 is probably a consequence of the episodic mass transfer from the less to the more massive component. Enhanced surface activity causes short-term apparent variations of the orbital period. The differences of times of the subsequent primary and secondary minima show two significant periodicities P_1 = 2.94 +/- 0.07 years and P_2 = 2.36 +/- 0.05 years. The latter periodicity is probably the beat period of the orbital and rotational period at the latitudes of most frequent occurrence of the spots.

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