RZ Leonis Minoris bridging between ER Ursae Majoris-type dwarf nova and nova-like system

• Published in: Publications of the Astronomical Society of Japan
• Main Authors: Kato, Taichi, Ishioka, Ryoko, Isogai, Keisuke, Kimura, Mariko, Imada, Akira, Miller, Ian, Masumoto, Kazunari, Nishino, Hirochika, Kojiguchi, Naoto, Kawabata, Miho, Sakai, Daisuke, Sugiura, Yuki, Furukawa, Hisami, Yamamura, Kenta, Kobayashi, Hiroshi, Matsumoto, Katsura, Wang, Shiang-Yu, Chou, Yi, Ngeow, Chow-Choong, Chen, Wen-Ping, Panwar, Neelam, Lin, Chi-Sheng, Hsiao, Hsiang-Yao, Guo, Jhen-Kuei, Lin, Chien-Cheng, Omarov, Chingis, Kusakin, Anatoly, Krugov, Maxim, Starkey, Donn R., Pavlenko, Elena P., Antonyuk, Kirill A., Sosnjvskij, Aleksei A., Antonyuk, Oksana I., Pit, Nikolai V., Baklanov, Alex V., Babina, Julia V., Itoh, Hiroshi, Padovan, Stefano, Akazawa, Hidehiko, Kafka, Stella, de Miguel, Enrique, Pickard, Roger D., Kiyota, Seiichiro, Shugarov, Sergey Yu, Chochol, Drahomir, Krushevska, Viktoriia, Sekeráš, Matej, Pikalova, Olga, Sabo, Richard, Dubovsky, Pavol A., Kudzej, Igor, Ulowetz, Joseph, Dvorak, Shawn, Stone, Geoff, Tordai, Tamás, Dubois, Franky, Logie, Ludwig, Rau, Steve, Vanaverbeke, Siegfried, Vanmunster, Tonny, Oksanen, Arto, Maeda, Yutaka, Kasai, Kiyoshi, Katysheva, Natalia, Morelle, Etienne, Neustroev, Vitaly V., Sjoberg, George
• Format: Journal Article
• Language: English
• Published: 27-10-2016
• ISSN: 0004-6264; 2053-051X
• DOI: 10.1093/pasj/psw101

Abstract We observed RZ LMi, which is renowned for its extremely short (∼19 d) supercycle and is a member of a small, unusual class of cataclysmic variables called ER UMa-type dwarf novae, in 2013 and 2016. In 2016, the supercycles of this object substantially lengthened in comparison to the previous measurements to 35, 32, and 60 d for three consecutive superoutbursts. We consider that the object virtually experienced a transition to the nova-like state (permanent superhumper). This observed behavior reproduced the prediction of the thermal-tidal instability model extremely well. We detected a precursor in the 2016 superoutburst and detected growing (stage A) superhumps with a mean period of 0.0602(1) d in 2016 and in 2013. Combined with the period of superhumps immediately after the superoutburst, the mass ratio is not as small as in WZ Sge-type dwarf novae, having orbital periods similar to RZ LMi. By using least absolute shrinkage and selection operator (Lasso) two-dimensional power spectra, we detected possible negative superhumps with a period of 0.05710(1) d. We estimated an orbital period of 0.05792 d, which suggests a mass ratio of 0.105(5). This relatively large mass ratio is even above that of ordinary SU UMa-type dwarf novae, and it is also possible that the exceptionally high mass-transfer rate in RZ LMi may be a result of a stripped secondary with an evolved core in a system evolving toward an AM CVn-type object.