Outburst Properties of Possible Candidates for Period Bouncers

This chapter presents the optical photometry of superoutbursts in the three WZ Sge-type dwarf novae ASASSN-15jd, ASASSN-16dt, and ASASSN-16hg. They commonly showed a luminosity dip in the middle of the plateau stage in their main superoutbursts. Also, it was confirmed that they have some observational features characteristic to the candidates for the period bouncer which has an extremely low-mass secondary star. We succeeded to estimate the binary mass ratio of ASASSN-16dt to be 0.036(2) by using stage A superhumps, which is much smaller than that of the systems at the period minimum. Summarizing these results, all of the three systems are possible candidates for the period-bouncer. The expected weak tidal effect by very low mass secondaries in these systems would be responsible for the slow growth of the tidal instability in the disk. We proposed that the luminosity dip in the plateau stage is attributed to the slow development of the eccentricity in the disk.