Discovery of a New Dwarf Nova, TSS J022216.4+412259.9: a WZ Sge-type Dwarf Nova Breaking the Shortest Superhump Period Record

We report on time-resolved CCD photometry of the newly-discovered dwarf nova, TSS J022216.4+412259.9 during its outburst in 2005 November- December. The best-estimated superhump period was 0.0554 days, which is the shortest superhump period among WZ Sge-type dwarf novae ever known. Double-peaked humps were also detected with a period of 0.05487 days in the early stage of the outburst. A rebrightening exhibited after the end of the plateau phase. All of these observations indicate the WZ Sge nature of the system. We mainly discuss the rebrightening stage of the superoutburst, compared with other WZ Sge-type dwarf novae.