Re: MASTER OT J055845.55+391533.4: new SU UMa-type dwarf nova

The resulting light curve clearly shows the presence of regular superhumps (4 in total) with an amplitude of 0.20 mag, establishing MASTER OT J055845.55+391533.4 as a new SU UMa-type dwarf nova.

The object is unusual in that it almost regularly showed a deep dip during past outbursts. There were sometimes variations like oscillations after the dip, and the overall behavior resembles a double superoutburst. 2018 Apr., 2019 Mar.-Apr., 2020 May, 2021 Jan.-Feb., 2021 Sep. all showed this feature. There was, however, no fading tail looking like an AM CVn star. The number of normal outbursts was smaller than that of superoutbursts. Please continue observing, since a dip is expected within a week. Recording variation of superhumps during the entire course of a superoutburst is very important to see what is happening.