New Bright CV detected by MASTER

ATel #5724; D. Denisenko, V. Lipunov, E. Gorbovskoy, P. Balanutsa, N. Tiurina, V. Kornilov, N. Shatskiy, V. Chazov, A. Kuznetsov, A. Rufanov, V. Vladimirov, V. Yecheistov (Moscow State University, SAI), V. Yurkov, Y. Sergienko, D. Varda, E. Sinyakov, A. Gabovich (Blagoveshchensk Educational University), A. Parkhomenko, A. Tlatov, D. Dormidontov, V. Senik (Kislovodsk Solar Station of Pulkovo Observatory), K. Ivanov, S. Yazev, N. Budnev, E. Konstantinov, O. Chuvalaev, V. Poleshchuk, O. Gress (Irkutsk State University), V. Krushinsky, I. Zalozhnih, A. Popov, A. Bourdanov (Ural Federal University), P. Podvorotny, V. Shumkov, S. Shurpakov (MASTER team members), H. Levato, C. Saffe (ICATE), C. Mallamaci, C. Lopez, F. Podest (OAFA)
on 5 Jan 2014; 12:02 UT
Credential Certification: Vladimir Lipunov (lipunov2007@gmail.com)

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MASTER OT J172758.09+380021.5 - new bright CV

MASTER-Amur auto-detection system discovered OT source at (RA, Dec) = 17h 27m 58.09s +38d 00m 21.5s on 2014-01-04.84034 UT. The OT unfiltered magnitude is 14.3m (limit 17.8m). The OT is seen in 11 images. There is no minor planet at this place. We have unfiltered reference image with OT at 17.7m on 2011-06-02.87014 UT (limit 19.6m). The object was observed in outbursts to 14.1m on 2012-09-20.465 and 2012-09-20.496 UT, then to 14.8m on a single MASTER-Amur image on 2013-02-25.849 UT, but was not detected as a transient then.

The OT at quiescence is identical to the blue star USNO-A2.0 1275-09374556 (17 27 58.19 +38 00 22.5 R=17.6 B=17.2) = USNO-B1.0 1280-0316081 (17 27 58.131 +38 00 22.78 pmRA=-12 pmDE=6 B1=17.98 R1=17.96 B2=17.10 R2=18.20 I=17.72). The star was in outburst on 1996-07-17 infrared DSS plate and at quiescence on other Palomar plates. SDSS has observed the star in a bright state as SDSS J172758.13+380022.4 (u=15.62 g=15.35 r=15.55 i=15.71 z=15.84). There is also an UV counterpart with two entries in GALEX data: GALEX J172758.0+380021 (FUV=17.36+/-0.05 NUV=17.58+/-0.03) and GALEX J172758.1+380022 (FUV=17.34+/-0.04 NUV=17.74+/-0.03).

There is nothing at this position in 1RXS, 2MASS, GCVS and AAVSO VSX. There is a radio source FIRST J172758.2+380019 with the peak flux of 1.01 mJy at 1.4 GHz formally 2.5" away, but with the error ellipse 9.3"x5.8". The object is listed in the atlas of Radio/X-ray associations (Flesch, 2010) with a 17% probability of being a QSO and 74% - a galaxy, despite the non-zero proper motion in USNO-B1 (-12, 6 mas/yr). We note there is another stellar object (SDSS J172758.28+380026.9 with g=20.3, r=19.9) 6" to the north of the OT. It is not clear whether MASTER OT J172758.09+380021.5 or the second object is a source of radio emission.

This area of sky in Hercules was observed by Catalina Sky Survey (Drake et al. 2009, ApJ, 696, 870) with 348 detections from 2005 June 05 to 2013 Sep. 23. At least 7 outbursts were detected, the brightest of them (14.3m) on 2011 Oct. 23. The star is about 18.0m at minimum brightness. The light curve is available at CRTS website: CSS J172758.1+380023.

Based on the blue color, proper motion, UV detection, amplitude of variability and archival light curve MASTER OT J172758.09+380021.5 is definitely a cataclysmic variable (dwarf nova in outburst). Follow up optical, radio and X-ray observations are required. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/172758.09380021.5.png

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