Spectroscopic and Photometric Observations of Dwarf Nova Superoutbursts by the 3.8 m Telescope Seimei and the Variable Star Network

Yusuke Tampo, Keisuke Isogai, Naoto Kojiguchi, Hiroyuki Maehara, Kenta Taguchi, Taichi Kato, Mariko Kimura, Yasuyuki Wakamatsu, Masaaki Shibata, Daisaku Nogami, Miho Kawabata, Keiichi Maeda, Kosuke Namekata, Soshi Okamoto, Masaaki Otsuka, Burgaz Umut, Shumpei Nagoshi, Hiroshi Itoh, Tonny Vanmunster, Tamas Tordai, Geoffrey Stone, Katsura Matsumoto, Daiti Fujii, Ryota Matsumura, Momoka Nakagawa, Nodoka Takeuchi, Yuki Zenkou, Elena P. Pavlenko, Kirill A. Antonyuk, Nikolaj V. Pit, Oksana I. Antonyuk, Julia V. Babina, Aleksei V. Baklanov, Aleksei A. Sosnovskij, Sergey Yu. Shugarov, Nataly Katysheva, Drahomir Chochol, Shawn Dvorak, Pavol A. Dubovsky, Tomas Medulka, Igor Kudzej, Seiichiro Kiyota, Alexandra M. Zubareva, Alexandr A. Belinski, Natalia P. Ikonnikova, Marina A. Burlak, Yasuo Sano, Masanori Mizutani, Javier Ruiz, Roger D. pickard, Franz-josef, Hambsch, Sjoerd Dufoer, Stephen M. Brincat, Charles Galdies, Kenneth Menzies, Masayuki Moriyama, Mitsutaka Hiraga, Yutaka Maeda, Kenji Hirosawa, Masao Funada, Minoru Yamamoto

Published 2021-04-11Version 1

We present spectroscopic and photometric observations of 17 dwarf-nova superoutbursts obtained by KOOLS-IFU mounted on the 3.8 m telescope Seimei at Okayama Observatory of Kyoto University and through VSNET collaboration. Our spectroscopic observations for six outbursts were performed within 1 d from their optical peak. 11 objects (TCP J00590972+3438357. ASASSN-19ado, TCP J06073081-0101501, ZTF20aavnpug, ASASSN-19ady, MASTER OT J061642.05+435617.9, TCP J20034647+1335125, ASASSN-20kv, ASASSN-20kw, MASTER OT J213908.79+161240.2, and ASASSN-20mf) were previously unknown systems, and our observations enabled quick classification of their transient type. These results illustrate that Seimei telescope has the capability to conduct quick follow-up observations of unknown transients. Our photometric observations yielded that 11 objects are WZ Sge-type dwarf novae and their candidates, and the other six objects are SU UMa-type dwarf novae and their candidates. The He II 4686\AA~ emission line was clearly detected among ASASSN-19ado, TCP J06073081-0101501 and MASTER OT J213908.79+161240.2, whose association with a spiral arm structure in an accretion disk has been suggested in the previous studies. Our result suggests that a higher-inclination system shows a stronger emission line of He II 4686\AA, as well as larger-amplitude early superhumps.