GALEX J194419.33+491257.0: An unusually active SU UMa-type dwarf nova with a very short orbital period in the Kepler data

Abstract

We studied a background dwarf nova of KIC 11412044 in the Kepler public data and identified it with GALEX J194419.33+491257.0. This object turned out to be a very active SU UMa-type dwarf nova that has a mean supercycle of ∼150d and frequent normal outbursts with intervals of 4-10d. The object showed a strong persistent signal of the orbital variation with a period of 0.0528164(4)d (76.06 min) and superhumps with a typical period of 0.0548d during its superoutbursts. Most of the superoutbursts were accompanied by a precursor outburst. All these features are unusual for this very short orbital period. We succeeded in detecting an evolving stage of superhumps (stage A superhumps) and obtained a mass ratio of 0.141(2), which is unusually high for this orbital period. We suggest that the unusual outburst properties are a result of this high mass ratio. We suspect that this object is a member of the recently recognized class of cataclysmic variables (CVs) with a stripped core evolved secondary which are evolving toward AM CVn-type CVs. The present determination of the mass ratio by using stage A superhumps is the first case in such systems. © 2014 The Author.