CCD Photometry of a Newly Confirmed SU UMa-Type Dwarf Nova, NSV 4838

Abstract

Abstract We present time-resolved CCD photometry of a dwarf nova, NSV 4838 (UMa 8, SDSS J102320.27$+$440509.8), during 2005 June and 2007 February outbursts. The two light curves showed superhumps with mean periods of 0.0699(1)d for the 2005 outburst and 0.069824(83)d for the 2007 outburst. Using its known orbital period of 0.0678 d, we estimated the mass ratio of the system to be $q$$=$ 0.13 based on an empirical relation. Although the majority of SU UMa-type dwarf novae having similar superhump periods show negative period derivatives, we found that the superhump period increased at $\dot{P}/P_{\rm sh}$$=$$+$7($+$3, $-$4) $\times$ 10$^{-5}$ during the 2007 superoutburst. We also investigated long-term light curves of NSV 4838, from which we derived 340 d as a supercycle of this system.