1996A&AS..118..421S

The analysis of the historical light curve revealed several kinds of variations not connected with the orbital modulation: a) large outbursts consisting of a primary (amplitude about 2mag_ vis._) and a fainter secondary peak; b) transitions from the high to the low state and vice versa; c) small outbursts (amplitude about 0.7mag_vis.) on the time scale of 15-20 days in the high state; d) year-to-year variations of brightness. It is shown that drastic changes of the photometric activity occurred in the course of the last six decades. An interpretation of this activity in terms of mass transfer events in a strongly interacting binary containing an accreting white dwarf is offered.