IW And-Type State in IM Eridani
Abstract
IW And stars are a recently recognized group of dwarf novae which are characterized by a repeated sequence of brightening from a standstill-like phase with damping oscillations followed by a deep dip. Kimura et al. (2019) recently proposed a model based on thermal-viscous disk instability in a tilted disk to reproduce the IW And-type characteristics. IM Eri experienced the IW And-type phase in 2018 and we recorded three cycles of the (damping) oscillation phase terminated by brightening. We identified two periods during the IW And-type state: 4-5 d small-amplitude (often damping) oscillations and a 34-43 d long cycle. This behavior is typical for an IW And-type star. The object gradually brightened within the long cycle before the next brightening which terminated the (damping) oscillation phase. This observation agrees with the increasing disk mass during the long cycle predicted by a model of thermal-viscous disk instability in a tilted disk (Kimura et al. 2019). We, however, did not succeed in detecting negative superhumps, which are considered to be the signature of a tilted disk.
Keywords
Cite
@article{arxiv.1911.01587,
title = {IW And-Type State in IM Eridani},
author = {Taichi Kato and Yasuyuki Wakamatsu and Naoto Kojiguchi and Mariko Kimura and Ryuhei Ohnishi and Keisuke Isogai and Keito Niijima and Tomohiro Yoshitake and Yuki Sugiura and Sho Sumiya and Daiki Ito and Kengo Nikai and Hanami Matsumoto and Katsura Matsumoto and Tonny Vanmunster and Franz-Josef Hambsch and Hiroshi Itoh and Julia V. Babina and Oksana I. Antonyuk and Alex V. Baklanov and Elena P. Pavlenko and Berto Monard and Shawn Dvorak},
journal= {arXiv preprint arXiv:1911.01587},
year = {2020}
}
Comments
6 pages, 3 figures, si.pdf (supporting information), accepted for publication in PASJ