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

• Published in: Publications of the Astronomical Society of Japan 2014-12, Vol.66 (6)
• Main Authors: Pavlenko, Elena P., Kato, Taichi, Antonyuk, Oksana I., Ohshima, Tomohito, Hambsch, Franz-Josef, Antonyuk, Kirill A., Sosnovskij, Aleksei A., Baklanov, Alex V., Shugarov, Sergey Yu, Pit, Nikolaj V., Nakata, Chikako, Masi, Gianluca, Nakajima, Kazuhiro, Maehara, Hiroyuki, Dubovsky, Pavol A., Kudzej, Igor, Andreev, Maksim V., Kuznyetsova, Yuliana G., Vasiliskov, Kirill A.
• Format: Article
• Language: English
• ISSN: 0004-6264; 2053-051X
• DOI: 10.1093/pasj/psu099

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.