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Discovery of a high-amplitude variability of the SU UMa dwarf nova = 1RXS J105120.5+672550 in quiescence

ATel #3889; E. Pavlenko (CrAO, Ukraine), T. Kato (Kyoto Univerity, Japan), N. Pit (CrAO, Ukraine), A. Baklanov (CrAO, Ukraine), K. Antonyuk (CrAO, Ukraine), W. Stein (New Mexico, USA).
on 26 Jan 2012; 14:23 UT
Credential Certification: E. Pavlenko (pavlenko@crao.crimea.ua)

Subjects: Optical, Binary, Cataclysmic Variable, Star, Variables

K. Sokolovsky and D. Denisenko detected a likely variable star during the search of new CVs from USNO-B1.0: Stars with Outbursts on IR Palomar Plates (cf. VSNET-alert 14060; arxiv:1108.5122). An outburst of this object was independently discovered by MASTER-Amur auto-detection system (MASTER OT105123.02+672528.3, (Atel #3845)) at V=14.6 mag and CATALINA robotic telescope (CSS120101:105123+672528, Drake et al., 2009, ApJ 696, 870) at 15.1 mag , VSNET alert 14055).

Its quiescent magnitude is about 18.5 - 19 (VSNET-alert 3845, VSNET-alert 14060). The brightness variations with period 0.06103(5) d and mean amplitude 0.08 mag that are believed to be positive superhumps, were found for the data obtained on Jan. 3 and 4 by A. Baklanov, E. Pavlenko and W. Stein (VSNET-alert 14067, VSNET-alert 14072 ). K. Sokolovsky et al. (ATel #3849) reported that no variability of this object exceeded 0.06 mag was found on Jan, 6.

We have observed this star on Jan. 19 with 1.25-m telescope of the Crimea astrophysical observatory equipped by CCD FLI 1001E in unfiltered light. Using R values of neighbor stars (D.G. Monet, 1998, BAAS 30, 1427), we found that during 4.8 hours of the observations, OT J105122.8+672528 displayed a variability in a wide range of 17.2 - 18.2 mag. (Fig.1). This variability consisted of the 0.0596(9) d period (Fig. 2) superimposed on the more long-term trend. The shape of original humps is different from cycle to cycle, the dips in hump's maxima up to 0.3 mag could occur. The mean amplitude of the 0.0596 d period is 0.4 mag (Fig. 3). This period is likely the orbital one, it perfectly fits to the "epsilon-orbital period" relation, where epsilon = (Psh - Porb)/Porb (Patterson, 1998, PASP 110, 1026) for the SU UMa stars.

Further studies of this object are encouraged. Figures 1, 2, 3 could be seen here:

http://s018.radikal.ru/i502/1201/08/1c2a47b8ded0.jpg

http://s018.radikal.ru/i520/1201/3b/56859ac45a65.jpg

http://s60.radikal.ru/i167/1201/ca/b2053bee4d01.jpg