Multicolor Photometry of an Outburst of a New WZ Sge-Type Dwarf Nova, OT J012059.6+325545

Abstract

Abstract We present our photometric studies of a newly discovered optical transient, OT J012059.6$ +$ 325545, which underwent a large outburst during the period between 2010 November and 2011 January. The amplitude of the outburst was $ \sim$ 8 mag. We performed simultaneous multicolor photometry using g$ '$-, $ R_{\rm C}$-, and $ i'$-band filters from the early stage of the outburst. Time-resolved photometry during its early stage revealed periodic variations with double-peaked profiles, which are referred to as early superhumps, with amplitudes of $ \sim$ 0.08 mag. After rapid fading in the main outburst, we found rebrightening phenomena, which occurred at least nine times. The large amplitude of the outburst, early superhumps, and rebrightening phenomena are typical features of WZ Sge-type dwarf novae. We detected color variations within early superhump modulations, which established this objects as the second system of WZ Sge-type dwarf nova, next to V445 And. We carried out numerical calculations of the accretion disk to explain both of the modulations and the color variations of the early superhump. This modeling of the disk height supports the idea that height variations within the outer disk can produce early-superhump modulations, though we cannot rule out an idea that temperature asymmetry may also play a role.