Long-Term Activity of a Little Known Dwarf Nova DT Octantis

Abstract

We analyze the long-term activity of a little known dwarf nova (DN) DT Oct. We use photographic observations from the Bamberg Observatory (Southern Patrol Photographic Sky Survey), CCD data from ASAS-3 survey, and AAVSO data (both CCD and visual). We determined the recurrence times of the superoutbursts, T_Cso, and of the normal outbursts, T_Cno, to be approximately 311 d and about 30 d, respectively. Although the length of T_Cso evolves gradually and undergoes only small variations (increases and decreases) of the nearby or neighbouring events (on the timescale of a few epochs), the evolution of T_Cso displays considerably larger changes on the longer timescales. They suggest a dominant trend of a decrease of T_Cso on the timescale of tens of years. The possibly magnetized white dwarf does not prevent DT Oct to show the long-term activity of the SU UMa systems. We place the time evolution of the superoutbursts of DT Oct in the context of DNe of various sub-types.