An ER Ursae Majoris star is a variety of SU Ursae Majoris star (a type of dwarf nova) in which the interval between super-outbursts is unusually short. ER UMa stars typically spend a third to a half their time in super-outburst, with a super-cycle (the interval between super-outbusts) of only 20 to 50 days. When not in super-outburst these stars show frequent normal outbursts – about one every 4 days.