fabrika@sao.ru

ATel #3352; S. Fabrika, E. Barsukova (Special Astrophysical Observatory, Russia), V. Goranskij (Sternberg Astronomical Institute, Russia), T. Kato, T. Ohshima (Kyoto University, Japan), D. Makarov, R. Uklein (Special Astrophysical Observatory, Russia), E. Pavlenko (Crimean Observatory, Ukraine)
on 15 May 2011; 21:51 UT
Credential Certification: Sergei Fabrika (fabrika@sao.ru)

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The CRTS Transient (Drake et al. 2009, ApJ, 696, 870), ID CSS110402:135906+554432 has brightened in March - April 2011, it reached 17.14 mag in unfiltered images on 2011 Apr. 2.34 UT, in its normal state it is fainter than 19 mag ( http://nesssi.cacr.caltech.edu/catalina/20110402/1104021550454132704.html#table1 ). The object is associated with known variable star DR UMa, its SDSS magnitudes are u = 20.56, g = 20.39, r = 19.99, i = 19.98, z = 19.95, the SDSS coordinates are 13 59 05.74, 55 44 29.58 (2000). We have taken 15-min spectrum of DR UMa with the SCORPIO spectrograph of the 6-meter Russian telescope on 2011 Apr. 13.88 UT. Spectral resolution was 13 A, however the spectrum was subjected to a strong Moon background. We find DR UMa is a QSO with a redshift z = 1.01 based on a broad emission line at ~ 5630 A, which we identify with MgII 2798 A, its EW is 30 A. A comparison with SDSS QSO template spectra http://www.sdss.org/gallery/gal_zqso.html reveals possible C III] 1908 A emission at our spectral range edge and other fainter emission lines. Strong absorption features at 4268, 5022/5045 and 5431 A may be MgII absorption lines arising in line of sight material. Using our calibrated spectrum we find B-V = 0.37, V-Rc = 0.39. In SCORPIO images taken before the spectroscopy (Apr. 13.87 UT) we estimate V = 19.04 +/- 0.05, where we used a nearby standard star (GSC 3855.1081 135911.73 +554413.0 (2000.0)) with about the same SDSS colors and found for this star V = 15.25. We have obtained unfiltered brightness estimates as 17.78 (Apr. 13.718 UT) and 17.88 (Apr. 16.732 UT) with the Kyoto University campus 40-cm telescope. The object is faint in the SDSS and in POSS2/UKSTU_BLUE images, but it is very bright in the POSS1_BLUE (dss1) images. The first mention of the star was in G. Romano, IBVS N1674, 1979 as an UG candidate (max 17.5B, min <18.2B, +0.1 < B-V < +0.5) based on 27 B and 17 V plates taken from 1970 to 1977. The second one was in the General Catalogue of Variable Stars (Samus et al., Astron. Lett., 29, 468, 2003) where it was named DR UMa. The third mention was in the Catalog and Atlas of Cataclysmic Variables (Downes et al., PASP, 109, 345, 1997), (DR UMa = GR 296). Romano published only rough coordinates but provided a finding chart. Following this chart, Downes et al. marked a blank place in their finding chart, and published coordinates which are ~ 26" to south from the CRTS transient. However in electronic version of the Downes et al. catalog http://archive.stsci.edu/prepds/cvcat a correct position of the CRTS transient is shown and noted that the "flagged object is extremely blue [(U-B)=-0.7, V=19.9], although it is 25" north of the nominal position (J. Thorstensen, private communication)". We propose then to identify the CRTS transient with DR UMa. This object is well-known radio source listed in different cataloques, the GPS candidate source ( http://vizier.u-strasbg.fr/viz-bin/VizieR ). Taking into account the optical flaring activity we suggest DR UMa is a blazar. DR UMa is very interesting for further studies.

Spectrum of DR UMa (7-pixel smoothed version of the spectrum shown in red)