Photometry of V1062 Tau: low states, short outbursts and period switching

Abstract

Time-resolved photometry of the long-period intermediate polar V1062 Tau confirmed the presence of the previously reported orbital and spin periods, and revealed the presence of a third one, corresponding to the beat of the two. While the orbital periodicity was present throughout our data, only one of the shorter periods was detectable at any given time. On a time-scale of ∼90 d, the short-period modulation in the light curve of the star changed three times between the spin period and the beat. On longer time-scales, we report two outbursts of V1062 Tau (the first to be recorded for this object) – both of which were probably short, low-amplitude bursts (Δm∼ 1.2 mag). Our data also suggest a brief low-state phase in 2002 January. Thus, this system joins two exclusive groups of intermediate polars: those undergoing short outbursts, and those having low states. We propose that the alternations between the short periods that modulate the light curve were caused by changes in the accretion mode, from disc-fed accretion to disc-overflow accretion. We further suggest that these changes may have been triggered by changes in mass-transfer rate, which were manifested by the low-state/outburst activity of the system.