Several SU UMa-type dwarf novae , in particular , WZ Sge-type stars tend to exhibit rebrightenings after superoutbursts .
The rebrightening phenomenon is problematic for the disk instability theory of dwarf novae since it requires a large amount of remnant matter in the disk even after superoutbursts .
Here , we report our optical and infrared observations during the first-ever outburst of a new dwarf nova , SDSS J102146.44 + 234926.3 .
During the outburst , we detected superhumps with a period of 0.056281 \pm 0.000015 { d } , which is typical for superhump periods in WZ Sge stars .
In conjunction with the appearance of a long-lived rebrightening , we conclude that the object is a new member of WZ Sge stars .
Our observations , furthermore , revealed infrared behaviors for the first time in the rebrightening phase of WZ Sge stars .
We discovered prominent infrared superhumps .
We calculate the color temperature of the infrared superhump source to be 4600—6400 K. These temperatures are too low to be explained with a fully-ionized disk appearing during dwarf nova outbursts .
We also found a K _ { s } -band excess over the hot disk component .
These unprecedented infrared activities provide evidence for the presence of mass reservoir at the outermost part of the accretion disk .
We propose that a moderately high mass-accretion rate at this infrared active region leads to the long-lived rebrightening observed in SDSS J102146.44 + 234926.3 .