[vsnet-outburst 15943] KIC 7524178

[Taichi Kato]

   I call you attention to this CV in the Kepler field.

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http://arxiv.org/abs/1309.1234

arXiv:submit/0794502
From: Taichi Kato <tkato at kusastro.kyoto-u.ac.jp>
Date: Thu, 5 Sep 2013 01:13:55 EST   (1086kb)

Title: KIC 7524178 -- an SU UMa-Type Dwarf Nova Showing Predominantly Negative
  Superhumps throughout Supercycle
Authors: Taichi Kato (Kyoto U.), Yoji Osaki (U. of Tokyo)
Categories: astro-ph.SR
Comments: 6 pages, 6 figures, accepted for publication in PASJ (Letters)
License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
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  We analyzed the Kepler long cadence data of KIC 7524178 (=KIS
J192254.92+430905.4), and found that it is an SU UMa-type dwarf nova with
frequent normal outbursts. The signal of the negative superhump was always the
dominant one even during the superoutburst, in contrast to our common knowledge
about superhumps in dwarf novae. The signal of the positive superhump was only
transiently seen during the superoutburst, and it quickly decayed after the
superoutburst. The frequency variation of the negative superhump was similar to
the two previously studied dwarf novae in the Kepler field, V1504 Cyg and V344
Lyr. This is the first object in which the negative superhumps dominate
throughout the supercycle. Nevertheless, the superoutburst was faithfully
accompanied by the positive superhump, indicating that the tidal eccentric
instability is essential for triggering a superoutburst. All the pieces of
evidence strengthen the thermal-tidal instability as the origin of the
superoutburst and supercycle, making this object the third such example in the
Kepler field. This object had unusually small (~1.0 mag) outburst amplitude and
we discussed that the object has a high mass-transfer rate close to the thermal
stability limit of the accretion disk. The periods of the negative and positive
superhumps, and that of the candidate orbital period were 0.07288 d (average,
variable in the range 0.0723-0.0731 d), 0.0785 d (average, variable in the
range 0.0772-0.0788 d) and 0.074606(1) d, respectively.