■ [dwarf nova] J2138+26: a rapid fading stopped
J2138+26 is a new WZ Sge-type dwarf nova, discovered by Dae-Am Yi on May 7 (CBET 2273). The superoutburst entered a rapid fading stage on May 30 (vsnet-alert 12013). The object is suggested to be similar to GW Lib, another WZ Sge star outbursting in 2007, in terms of a low inclination angle and apparent brightness.
We have monitored this object with standard optical and near-infrared imaging and high-speed photometry with a time-resolution of 1 sec. The upper figure shows the V and J-band light curves we obtained. The V-J color during the superoutburst is quite similar to that observed in GW Lib (V-J~-0.2 -- +0.1). The rapid fading was confirmed in our observation on 31 May. At the same time, the V-J color increased to ~0.8, which is also analogous to GW Lib at the same phase. The lower figure shows the result of our high-speed photometry on 31 May. The rapid fading trend seems to be stopped, and small humps with an amplitude of ~0.1 mag can be seen. In the case of GW Lib, the rapid fading was not stopped like J2138+26, and continued until it reached V~15 and V-J~1.5.
The termination of the rapid fading implies that the object could experience a rebrightening in the next couple of days.