SDSS J080434.20+510349.2: Eclipsing WZ Sge-type Dwarf Nova with multiple rebrightenings

Abstract

We observed the 2006 superoutburst of SDSS J080434.20+510349.2 during its plateau phase, rebrightening phase, and post-superoutburst final decline. We found that this object is a grazing eclipsing system with a period of 0.0590048(2) d. Well-defined eclipses were only observed during the late stage of the superoutburst plateau and the depth decreased during the subsequent stages. We determined the superhump period during the super-outburst plateau to be 0.059539(11)d, giving a fractional superhump excess of 0.90(2)%. During the rebrightening and post-superoutburst phases, persisting superhumps have periods longer than those of superhumps during the plateau phase: 0.059632(6) d during the rebrightening phase and 0.05969(4) d during the final fading. This phenomenon is very well in line with the previously known long-period "late superhumps" in GW Lib, V455 And, and WZ Sge. The amplitudes of orbital humps between different states of rebrightenings suggest that these humps do not arise from the classical hot spot, but are more likely to be a result of projection effect in a high-inclination system. There was no clear evidence for an enhanced hot spot during the rebrightening phase. We also studied previously reported "mini-outbursts" in the quiescent state, and found evidence that superhumps were transiently excited during these mini-outbursts. The presence of grazing eclipses and distinct multiple rebrightenings in SDSS J080434.20+510349.2 would provide a unique opportunity for understanding the mechanism of rebrightenings in WZ Sge-type dwarf novae. ©2009. Astronomical Society of Japan.