ASASSN-18aan: An eclipsing SU UMa-type cataclysmic variable with a 3.6-hr orbital period and a late G-type secondary star

Wakamatsu, Y.; Thorstensen, J.R.; Kojiguchi, N.; Isogai, K.; Kimura, M.; Ohnishi, R.; Kato, T.; Itoh, H.; Sugiura, Y.; Sumiya, S.; Matsumoto, H.; Ito, D.; Nikai, K.; Akitaya, H.; Ishioka, C.; Oide, K.; Kanai, T.; Uzawa, Y.; Oasa, Y.; Tordai, T.; Vanmunster, T.; Shugarov, S.Y.; Yamanaka, M.; Sasada, M.; Takagi, K.; Nishinaka, Y.; Yamazaki, Y.; Otsubo, I.; Nakaoka, T.; Murata, K.L.; Ohsawa, R.; Morita, M.; Ichiki, M.; Dufoer, S.; Mizutani, M.; Horiuchi, T.; Tozuka, M.; Takayama, M.; Ohshima, T.; Saito, T.; Dubovsky, P.A.; Stone, G.; Miller, I.; Nogami, D.

Авторы: Wakamatsu Yasuyuki, Thorstensen John R., Kojiguchi Naoto, Isogai Keisuke, Kimura Mariko, Ohnishi Ryuhei, Kato Taichi, Itoh Hiroshi, Sugiura Yuki, Sumiya Sho, Matsumoto Hanami, Ito Daiki, Nikai Kengo, Akitaya Hiroshi, Ishioka Chihiro, Oide Kohei, Kanai Takahiro, Uzawa Yoshinori, Oasa Yumiko, Tordai Tamás, Vanmunster Tonny, Shugarov Sergey Yu, Yamanaka Masayuki, Sasada Mahito, Takagi Kengo, Nishinaka Yuki, Yamazaki Yuina, Otsubo Ikki, Nakaoka Tatsuya, Murata Katsuhiro L., Ohsawa Ryou, Morita Masahiro, Ichiki Makoto, Dufoer Sjoerd, Mizutani Masanori, Horiuchi Takashi, Tozuka Miyako, Takayama Masaki, Ohshima Tomohito, Saito Tomoki, Dubovsky Pavol A., Stone Geoff, Miller Ian, Nogami Daisaku
Журнал: Publications of the Astronomical Society of Japan
Том: 73
Номер: 5
Год издания: 2021
Издательство: Astronomical Society of Japan
Местоположение издательства: Japan
Первая страница: 1209
Последняя страница: 1224
DOI: 10.1093/pasj/psab003
Аннотация: We report photometric and spectroscopic observations of the eclipsing SU UMa-type dwarf nova ASASSN-18aan. We observed the 2018 superoutburst with 2.3 mag brightening and found the orbital period (Porb) to be 0.149454(3) d, or 3.59 hr. This is longward of the period gap, establishing ASASSN-18aan as one of a small number of long-Porb SU UMa-type dwarf novae. The estimated mass ratio, [q = M2/M1 = 0.278(1)], is almost identical to the upper limit of tidal instability by the 3 : 1 resonance. From eclipses, we found that the accretion disk at the onset of the superoutburst may reach the 3 : 1 resonance radius, suggesting that the superoutburst of ASASSN-18aan results from the tidal instability. Considering the case of long-Porb WZ Sge-type dwarf novae, we suggest that the tidal dissipation at the tidal truncation radius is enough to induce SU UMa-like behavior in relatively high-q systems such as SU UMa-type dwarf novae, but that this is no longer effective in low-q systems such as WZ Sge-type dwarf novae. The unusual nature of the system extends to the secondary star, for which we find a spectral type of G9, much earlier than typical for the orbital period, and a secondary mass M2 of around 0.18 M⊙, smaller than expected for the orbital period and the secondary’s spectral type. We also see indications of enhanced sodium abundance in the secondary’s spectrum. Anomalously hot secondaries are seen in a modest number of other CVs and related objects. These systems evidently underwent significant nuclear evolution before the onset of mass transfer. In the case of ASASSN-18aan, this apparently resulted in a mass ratio lower than typically found at the system’s Porb, which may account for the occurrence of a superoutburst at this relatively long period.
Добавил в систему: Шугаров Сергей Юрьевич

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ASASSN-18aan: An eclipsing SU UMa-type cataclysmic variable with a 3.6-hr orbital period and a late G-type secondary starстатья

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