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Chikako Nakata, Tomohito Ohshima, Taichi Kato, Daisaku Nogami, Gianluca Masi, Enrique de Miguel, Joseph Ulowetz, Colin Littlefield, William N. Goff, Thomas Krajci, Hiroyuki Maehara, William Stein, Richard Sabo, Ryo Noguchi, Rikako Ono, Miho Kawabata, Hisami Furukawa, Katsura Matsumoto, Takehiro Ishibashi, Pavol A. Dubovsky, Igor Kudzej, Shawn Dvorak, Franz-Josef HAMBSCH, Roger D. Pickard, Etienne Morelle, Eddy Muyllaert, Stefano Padovan, Arne Henden, WZ Sge-Type Dwarf Novae with Multiple Rebrightenings: MASTER OT J211258.65+242145.4 and MASTER OT J203749.39+552210.3, Publications of the Astronomical Society of Japan, Volume 65, Issue 6, 25 December 2013, 117, https://doi.org/10.1093/pasj/65.6.117
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Abstract
We report on photometric observations of two WZ Sge-type dwarf novae, MASTER OT J211258.65+242145.4 and MASTER OT J203749.39+552210.3, which underwent outbursts in 2012. Early superhumps were recorded in both systems. During the superoutburst plateau, ordinary superhumps with a period of 0.060291(4) d (MASTER J211258) and with 0.061368(11) d (MASTER J203749) on average were observed. MASTERJ211258 and MASTERJ203749 exhibited eight post-superoutburst rebrightenings and more than four, respectively. In the final part of the superoutburst, an increase in superhump period was seen in both systems. We made a survey of WZSge-type dwarf novae with multiple rebrightenings, and confirmed that the superhump periods of WZSge-type dwarf novae with multiple rebrightenings were longer than those of WZSge-type dwarf novae without a rebrightening. Although WZSge-type dwarf novae with multiple rebrightenings have been thought to be likely candidates for period bouncers based on their low mass ratio (q), inferred from the period of fully grown (stage B) superhumps, our new method of using the period of growing superhumps (stage A superhumps), however, implies higher q's than those expected from stage B superhumps. These q values appear to be consistent with the duration of the stage A superoutbursts, which likely reflects the growth time of the 3W1 resonance. We present a working hypothesis that the small fractional superhump excesses for stage B superhumps in these systems may be explained by a gas pressure effect that works more efficiently in these systems than in ordinary SU UMa-type dwarf novae. This result forms a new picture that WZSge-type dwarf novae with multiple rebrightenings and SU UMa-type ones without a rebrightening (they are not period bouncers) are located in the same place on the evolutionary track.
