Bright CV detected by MASTER and correction to ATel 5174

ATel #5182; D. Denisenko (SAI MSU/IRS), N. Voroshilov, A. Lazareva (International Research School, Moscow, Russia), V. Lipunov, E. Gorbovskoy, P. Balanutsa, N. Tiurina, V. Kornilov, N. Shatskiy, V. Chazov, A. Kuznetsov, V. Yecheistov (Moscow State University, SAI), V. Yurkov, Y. Sergienko, D. Varda, E. Sinyakov, A. Gabovich (Blagoveshchensk Educational University), V. Krushinsky, I. Zalozhnih, A. Popov, A. Bourdanov, A. Punanova (Ural Federal University), K. Ivanov, S. Yazev, N. Budnev, E. Konstantinov, O. Chuvalaev, V. Poleshchuk, O. Gress, A. Frolova (Irkutsk State University), A. Parkhomenko, A. Tlatov, D. Dormidontov, V. Senik (Kislovodsk solar station of the Pulkovo observatory RAS), P. Podvorotny, V. Shumkov, S. Shurpakov (MASTER team members), H. Levato, C. Saffe (ICATE), C. Mallamaci, C. Lopez and F. Podest (OAFA)
on 29 Jun 2013; 20:45 UT
Credential Certification: Vladimir Lipunov (lipunov2007@gmail.com)

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MASTER OT J174816.22+501723.3 - new CV

MASTER-Amur auto-detection system discovered OT source at (RA, Dec) = 17h 48m 16.22s +50d 17m 23.3s on 2013-06-28.64672 UT. The OT unfiltered magnitude is 15.6m (limit 18.4m). The OT is seen in 4 images. There is no minor planet at this place. We have reference image without OT on 2013-05-13.69463 UT with unfiltered magnitude limit 18.2m.

The object is identical to the blue star SDSS J174816.31+501723.3 (u=17.80 g=17.59 r=17.71 i=17.74 z=17.85). It is present in USNO-B catalogue as USNO-B1.0 1402-0303843 (17 48 16.316 +50 17 23.28 pmRA=6 pmDE=-10 B1=16.69 R1=16.46 B2=18.02 R2=18.43 I=16.10). There is also an infrared counterpart 2MASS 17481631+5017229 (J=15.55+/-0.06 H=15.45+/-0.11 K=15.61+/-0.21). This area of sky in Hercules is not covered by GALEX. Nothing is present at this position in 1RXS, GCVS and AAVSO VSX.

The object was observed many times by Catalina Sky Survey, but was not discovered as a transient. The light curve available from CRTS DR2 shows at least 5 outbursts, the brightest of them (15.5m) detected on MJD=54913 (2009 Mar. 23).

Based on the blue color, amplitude of variability (about 4m) and previous outbursts we conclude that MASTER OT J174816.22+501723.3 is a new cataclysmic variable (dwarf nova). SDSS colors suggest a very small contribution from the secondary component and the short orbital period. Follow up observations are required. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/174816.22501723.3.png

This OT was discovered during the Astronomy project at the Sixth International Research School (IRS-6) held in Moscow region. The School is supported by Moscow City Center of Children and Youth Creativity.

Corrigenda to ATel #5174

MASTER OT J070950.24+643802.9 found by V. Shumkov is not the real object but actually a group of hot pixels and should be discarded.

MASTER OT J182122.59+614854.8 found by V. Yecheistov is identical to ASASSN-13at (ATel #5168, Stanek et al.). The object was independently discovered by MASTER-Amur ~5 hours after ASAS-SN observations. It was already noted by S. Otero in [vsnet-alert 15881]. We apologize for any inconveniences it might have caused.

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