Discovery of a new IW And-type dwarf nova with both tilted disk and tidal instability
arxiv(2024)
摘要
IW And-type dwarf novae are anomalous Z Cam stars featured with outbursts
happening during standstill states, which are not expected in the standard disk
instability model. The physical mechanisms for these variations remain unclear.
In this study, we report the discovery of a new candidate IW And-type dwarf
nova J0652+2436, identified with its frequent outbursts from the slowly rising
standstill states. Luckily, the TESS observations during a long standstill
state and the earlier K2 observations give a chance to find the orbital and
negative superhump period in the light curve of J0652+2436, allowing the
measurement of its mass ratio of 0.366. This mass ratio is marginally possible
for the tidal instability to set in according to previous SPH simulations.
Thus, we propose that the outbursts in J0652+2436 are likely to be caused by
the growing accretion disk during standstills, in favor of the previous
hypothesis of the mechanisms lying in all IW And stars. We conclude that
J0652+2436 might be the first IW And star with both a precessing tilted disk
and tidal instability, which will be an important laboratory for studying the
accretion disk dynamics and help understand IW And phenomenon.
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