* Astronomy

Title: CCD Photometry of a Newly Confirmed SU UMa-Type Dwarf Nova, NSV 4838
Authors: Akira Imada, Tatsuki Yasuda, Toshihiro Omodaka, Shota Oizumi, Hiroyuki Yamamoto, Shunsuke Tanada, Yoshihiro Arao, Kie Kodama, Miho Suzuki, Takeshi Matsuo, Hiroyuki Maehara, Taichi Kato, Kei Sugiyasu, Yuuki Moritani, Masanao Sumiyoshi, Kazuhiro Nakajima, Johen Pietz, Kenshi Yanagisawa, Daisaku Nogami

We present time-resolved CCD photometry of a dwarf nova NSV 4838 (UMa 8, SDSS J102320.27+440509.8) during the 2005 June and 2007 February outburst. Both light curves showed superhumps with a mean period of 0.0699(1) days for the 2005 outburst and 0.069824(83) days for the 2007 outburst, respectively. Using its known orbital period of 0.0678 days, 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_{
m sh}=+7(+3, -4) x 10^{-5} during the 2007 superoutburst. We also investigated long-term light curves of NSV 4838, from which we derived 340 days as a supercycle of this system.

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