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.

中文翻译：

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IM Eridani 中的 IW And-type 状态

IW 和恒星是最近被认可的一组矮新星，其特征是从静止阶段重复增亮，伴随阻尼振荡，然后是深倾。木村等人。(2019) 最近提出了一个基于倾斜盘中热粘性盘不稳定性的模型，以重现 IW And 型特性。IM Eri 在 2018 年经历了 IW And 型阶段，我们记录了（阻尼）振荡阶段的三个周期，以增亮终止。我们在 IW And 型状态期间确定了两个时期：4-5 d 小幅度（通常是阻尼）振荡和 34-43 d 长周期。这种行为是 IW And 型恒星的典型特征。物体在长周期内逐渐变亮，然后下一次变亮终止（阻尼）振荡阶段。这一观察结果与倾斜盘中热粘性盘不稳定性模型预测的长周期中盘质量的增加一致（Kimura 等人，2019 年）。然而，我们没有成功检测到负的超级驼峰，这被认为是倾斜圆盘的特征。