[] J1028-08 : humps with a very short period, confirmed



OT J102842.9-081927 (J1028-08) was discovered by the Catalina Sky Survey on 31 March 2009. .

Due to the detection of possible superhumps with a quite short period (0.0381~d), the object is suspected to be a rare object, such as V485 Cen and EI Psc, or AM CVn stars (double-white dwarf system) (vsnet-alert 11149).

We performed time-series photometric observations of J1028-08 with KANATA last night (2 Apr). We confirmed the humps whose period is roughly consistent with the reported one. We found that the V-J color is quite blue (V-J~-0.6). The V-J color is usually between -0.2 and 0.2 in normal dwarf novae in superoutburst. In our past observations, CR Boo, an AM CVn star, exhibited a similar color during its superoutburst.

Although the S/N of our J-band data is low, phase-averaged light curves suggest that the hump amplitude is larger in V-band than that in J-band. The temperature of the hump component is probably higher than that of an underlying stationary component.