* Astronomy

Title: Multi-Colour Photometry of the Outburst of the New WZ Sge-type Dwarf Nova, OT J012059.6+325545
Authors: Shinichi Nakagawa, Ryo Noguchi, Eriko Iino, Kazuyuki Ogura, Katsura Matsumoto, Akira Arai, Mizuki Isogai, Makoto Uemura

We present our photometric studies of the newly discovered optical transient, OT J012059.6+325545, which underwent a large outburst between 2010 November and 2011 January. The amplitude of the outburst was about 8 mag. We performed simultaneous multi-colour photometry by using g', Rc, and i'-band filters from the early stage of the outburst. The time resolved photometry during the early stage revealed periodic variations with double-peaked profiles, which are referred to as early superhumps, with amplitudes of about 0.08 mag. After the rapid fading from 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 colour variations within the early superhump modulations making this only the second system, after V445 And, for which this has been established. We carried out numerical calculations of the accretion disk to explain both of the modulations and the colour variations of the early superhump. This modelling of the disk height supports the idea that height variations within the outer disk can produce the early superhump modulations, though we cannot rule out that temperature asymmetries may also play a role.

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