ASASSN-15jd: WZ Sge-type star with intermediate superoutburst between single and double ones

Abstract

We present optical photometry of a WZ Sge-type dwarf nova (DN), ASASSN-15jd. Its light curve showed a small dip in the middle of the superoutburst in 2015 for the first time among WZ Sge-type DNe. The unusual light curve implies a delay in the growth of the 3:1 resonance tidal instability. Also, the light curve is similar to those of other two WZ Sge-type stars, SSS J122221.7$-$311523 and OT J184228.1$+$483742, which are believed to be the best candidates for a period bouncer on the basis of their small values of the mass ratio ($q\equiv M_2/M_1$). Additionally, the small mean superhump amplitude ($<$ 0.1 mag) and the long duration of no ordinary superhumps at the early stage of the superoutburst are common to the best candidates for a period bouncer. The average superhump period was $P_{\mathrm{sh}}$ = 0.0649810(78) d and no early superhumps were detected. Although we could not estimate the mass ratio of ASASSN-15jd with high accuracy, this object is expected to be a candidate for a period bouncer, a binary accounting for the missing population of post-period minimum cataclysmic variables, based on the above characteristics.

arXiv comment11 Pages, 10 Figures, 4 Tables, accepted for publication in PASJ (includes supporting information)

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• NSV 1440: First WZ Sge-type Object in AM CVn stars and candidates
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• TCP J07222683$+$6220548: a new AM CVn type system with infrequent outbursts
• Photometric Analysis of TCP J20171288$+$1156589 -- WZ Sge Type Dwarf Nova with Delayed Ordinary Superhumps Emergence