We report the observation of a new dwarf nova , OT J055717 + 683226 , during its first-ever recorded superoutburst in December 2006 .
Our observation shows that this object is an SU UMa-type dwarf nova having a very short superhump period of 76.67 \pm 0.03 { min } ( 0.05324 \pm 0.00002 { d } ) .
The next superoutburst was observed in March 2008 .
The recurrence time of superoutbursts ( supercycle ) is , hence , estimated to be \sim 480 { d } .
The supercycle is much shorter than those of WZ Sge-type dwarf novae having supercycles of \gtrsim 10 { yr } , which are a major population of dwarf novae in the shortest orbital period regime ( \lesssim 85 { min } ) .
Using a hierarchical cluster analysis , we identified seven groups of dwarf novae in the shortest orbital period regime .
We identified a small group of objects that have short supercycles , small outburst amplitudes , and large superhump period excesses , compared with those of WZ Sge stars .
OT J055717 + 683226 probably belongs to this group .