The peculiar binary V Sagittae: Properties of its long-term light changes^*

¹ Astronomical Institute, Academy of Sciences, 251 65 Ondřejov, Czech Republic
² AAVSO, 25 Birch Street, Cambridge, Massachusetts, 02138-1205, U.S.A.

Send offprint request to: V. Šimon

Received: 28 September 1998
Accepted: 9 June 1999

Abstract

Analysis of the AAVSO and AFOEV visual data (more than 6000 one-day means) revealed that V Sge displayed intervals of the suppressed brightness variations (flat segments), interchanging with intervals of the pronounced changes (active segments). The borderlines of the segments are sharp and are just several days long while the length of the segment is several years. The character of the brightness variations in the active segments evolves and depends on the mean level of brightness in the given segment. The low level gives rise to the separated relatively narrow outbursts while the high state/low state transitions occur in segments with higher mean brightness. We discuss the long-term activity in terms of the divergent models for V Sge and conclude that the mass accreting white-dwarf primary and variable mass transfer offer a viable explanation for the photometric activity of V Sge. Our analysis therefore brings an additional support to the model by [Williams et al. (1986)] and [Patterson et al. (1998).]