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ATEL # 1938; V.P.Goranskij and N.V.Metlova (SAI, Moscow Univ.)
on 23 Feb 2009; 14:42 UT
Password Certification: Vitaly Goranskij (email@example.com)
Subjects: Optical, Binaries, Nova, Transients, Variables
Referred to by ATEL #: 1940
We report the results of photometric BVRc monitoring of soft X-ray transient and possible O/Ne class nova CSS 081007:030559+054715 (ATEL #1825, ATEL #1835, ATEL #1847, ATEL #1873, ATEL #1910). Using 60-cm telescope of SAI Crimean Station (Ukraine) and CCD Apogee-47, we have taken 211 V band observations in 13 nights in the time range between 2008 Dec 3 and 2009 Feb 19. We have also a few observations in the B and Rc bands. The comparison star was GSC 0061.1376 (3:05:53.5 +5:46:26, 2000; v=15.1), the following magnitudes were determined by us for it: B,V,Rc = (15.69,15.00,14.48). We measured also 5 check stars in the vicinity of the nova. The accuracy of observations is 0.02 mag (excluding one night 2008 Dec 11 when the accuracy was 0.06 mag due to close moon location). The brightness of the nova varied between 16.01 and 17.07 mag in V band, its colours were B-V=-0.08+/-0.04 and V-Rc=+0.20+/-0.07. The light curve of nova displays 50-day long plateau at the level of 16.3 V finished on 2009 Jan 22 and subsequent rapid decay. The amplitude of variations during plateau was 0.40 mag.
Our observations do not confirm Swift 1.77 day period reported in ATEL #1873 based on X-ray and UV observations. Although, a nearby value of period, 1.694+/-0.005 day presents the light curve very similar to X-ray one described there. Analysing 203 observations in the plateau stage with the Lafler-Kinman PDM method, we found also a possible period 0.6106+/-0.0006 day with the asymmetric light curve resembling the light curves of novae CI Aql and V723 Cas passed through SSS phase. The mean amplitudes of light curves with these two periods are of about 0.25 mag. Both periodic solutions include some essential contradicted observations and should be verified with additional photometric data if available. So, we made our original tables of observations accessible in Internet .