NY Serpentis: SU UMa-type nova in the period gap with diversity of normal outbursts

We present a photometric study of NY Ser, an in-the-gap SU UMa-type nova, in 2002 and 2013. We determined the duration of its superoutburst and the mean period of its superhump are 18 d and 0.10458 d, respectively. We detected in 2013 that NY Ser showed two distinct states separated by a superoutburst. A state of rather infrequent normal outbursts lasted at least 44 d before the superoutburst, and a state of frequent outbursts started immediately after the superoutburst and lasted at least 34 d. Unlike a typical SU UMa star with a bimodal distribution of outburst duration, NY Ser displayed a diversity of normal outbursts. In the state of infrequent outbursts, we detected a wide ∼ 12 d outburst accompanied by 0.098 d orbital modulation but without superhumps ever established in NY Ser. We classified this as a "wide normal outburst." The orbital period was dominant both in quiescence and during normal outbursts in this state. In the state of the most frequent normal outbursts, the 0.10465 d positive superhump period was dominant and coexisted with the orbital modulation. In 2002 we detected the normal outburst of "intermediate" 5-6 d duration that was also accompanied by orbital modulations.