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We report on time-resolved photometry of the 2015 February-March superoutburst of QZVirginis. The superoutburst consisted of a separated precursor, main superoutburst, and rebrightening. We detected superhumps with a period of 0.061181(42) d between the precursor and main superoutburst. Based on analyses of period changes and amplitudes of superhumps, the observed superhumps were identified as growing superhumps (stage A superhumps). The duration of the stage A superhumps was about 5 d, unusually long for SUUMa-type dwarf novae. Using the obtained stage A superhump period, we estimated the mass ratio of QZ Vir to be 0.108(3). This value suggests that QZ Vir is an SUUMa-type dwarf nova evolving toward the period minimum. Based on the present and previous observations regarding long-lasting stage A superhumps, the time scale for stage A superhumps is likely to be determined by the mass ratio of the system and the temperature of the accretion disk. [ABSTRACT FROM AUTHOR]

We observed the 2016 outburst of OT J002656.6+284933 (CSS101212:002657+284933) and found that it has the longest recorded [0.13225(1) d on average] superhumps among SUUMa-type dwarf novae. The object is the third known SUUMa-type dwarf nova above the period gap. The outburst, however, was unlike ordinary long-period SUUMa-type dwarf novae in that it showed two post-outburst rebrightenings. It showed superhump evolution similar to short-period SUUMa-type dwarf novae. We could constrain themass ratio to less than 0.15 (most likely between 0.10 and 0.15) by using superhump periods in the early and post-superoutburst stages. These results suggest the possibility that OT J002656.6+284933 has an anomalously undermassive secondary and it should have followed a different evolutionary track from the standard one. [ABSTRACT FROM AUTHOR]

We observed the 2015 July-August long outburst of V1006 Cyg and established this object to be an SUUMa-type dwarf nova in the period gap. Our observations have confirmed that V1006 Cyg is the second established object showing three types of outbursts (normal, long normal, and superoutbursts) after TUMen. We have succeeded in recording the growing stage of superhumps (stage A superhumps) and obtained a mass ratio of 0.26-0.33, which is close to the stability limit of tidal instability. This identification of stage A superhumps demonstrates that superhumps indeed slowly grow in systems near the stability limit, the idea first introduced by Kato et al. (2014, PASJ, 66, 90). The superoutburst showed a temporary dip followed by a rebrightening. The moment of the dip coincided with the stage transition of superhumps, and we suggest that stage C superhumps are related to the start of the cooling wave in the accretion disk. We interpret that the tidal instability was not strong enough to maintain the disk in the hot state when the cooling wave started. We propose that the properties commonly seen in the extreme ends of mass ratios (WZ Sge-type objects and long-period systems) can be understood as a result of weak tidal effect. [ABSTRACT FROM AUTHOR]

In 2015 March, the notable WZSge-type dwarf nova ALCom exhibited an unusual outburst with a recurrence time of ~1.5 yr, which is the shortest interval of superoutbursts among WZSge-type dwarf novae. Early superhumps in the superoutburst light curve were absent, and a precursor was observed at the onset of the superoutburst for the first time in WZSge-type dwarf novae. The present superoutburst can be interpreted as a result of the condition that the disk radius barely reached the 3:1 resonance radius, but did not reach the 2:1 resonance one. Ordinary superhumps immediately grew following the precursor. The initial part of the outburst is indistinguishable from those of superoutbursts of ordinary SUUMa-type dwarf novae. This observation supports the interpretation that the 2:1 resonance suppresses a growth of ordinary superhumps. The estimated superhump period and superhump period derivative are Psh = 0.0573185(11) d and Pdot=+1.5(3.1)?10-5, respectively. These values indicate that the evolution of ordinary superhumps is the same as that in past superoutbursts with much larger extent. Although the light curve during the plateau stage was typical for an SUUMa-type dwarf nova, this superoutburst showed a rebrightening, together with a regrowth of the superhumps. The overall light curve of the rebrightening was the almost the same as those observed in previous rebrightenings. This implies that the rebrightening type is inherent in the system. [ABSTRACT FROM AUTHOR]