Two bright CVs detected by MASTER

ATel #4843; V. Yecheistov, D. Denisenko, V. Lipunov, E. Gorbovskoy, N. Tiurina, P. Balanutsa, V. Kornilov, A. Belinski, N. Shatskiy, V. Chazov, A. Kuznetsov, D. Zimnukhov (Moscow State University, SAI), 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), V. Yurkov, Y. Sergienko, D. Varda, E. Sinyakov (Blagoveshchensk Educational University), P. Podvorotny, V. Shumkov, S. Shurpakov (MASTER team members), H. Levato, C. Saffe (ICATE), C. Mallamaci, C. Lopez and F. Podest (OAFA)
on 27 Feb 2013; 00:25 UT
Credential Certification: Vladimir Lipunov (lipunov2007@gmail.com)

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MASTER OT J073418.66+271310.5 - new bright CV

MASTER-Amur auto-detection system discovered OT source at (RA, Dec) = 07h 34m 18.66s +27d 13m 10.5s on 2013-02-25.61545 UT. The OT unfiltered magnitude is 15.0m (limit 17.3m). The OT is seen in 3 images. There is no minor planet at this place. We have reference image without OT on 2013-02-02.57894 UT with unfiltered magnitude limit 18.7m.

The object is identical to the blue star SDSS J073418.67+271309.4 (u=19.82 g=20.29 r=19.96 i=19.81 z=19.78) which is present in other catalogs as USNO-B1.0 1172-0186162 (B1=19.82 R1=19.44 B2=20.40 R2=19.70 I=19.16) and USNO-A2.0 1125-05219166 (R=19.4 B=19.3). There is also an UV counterpart with 3 entries in GALEX data: GALEX J073418.8+271310 (FUV=21.82+/-0.34, NUV=21.69+/-0.34), J073418.8+271308 (FUV=20.84+/-0.34, NUV=21.03+/-0.27) and J073418.9+271309 (FUV=21.37+/-0.06, NUV=20.70+/-0.08).

There is nothing at this position in 1RXS, GCVS and AAVSO VSX. No previous outbursts were detected on 15 digitized POSS plates taken between 1953 and 2000, as well as on 30 Palomar/NEAT images obtained on 10 nights from 1997 Dec. 26 to 2003 Mar. 07. There are no previous outbursts in CRTS DR2 (CSS+MLS data). However, the star was detected in outburst on 2MASS infrared images taken on 1998 Jan. 26. It is present in 2MASS catalogue as 2MASS 07341868+2713095 with the following magnitudes: J=15.115+/-0.035, H=15.088+/-0.061, K=15.125+/-0.115. This is ~5m brighter than 2009 UKIDSS measurement (Y=19.82+/-0.10, J=20.07+/-0.18). Color-combined (JHK) chart from 2MASS images is uploaded to J073418+271310-JHK.jpg (8'x8' FOV). Position of 2MASS 07341868+2713095 is marked with dashes.

Based on the blue color and outburst amplitude we conclude that MASTER OT J073418.66+271310.5 is a new cataclysmic variable, most likely a dwarf nova of UGSU subtype.

Follow up observations are required. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/073418.66271310.5.png

MASTER OT J183007.03+764313.3 - new bright CV

MASTER-Amur auto-detection system discovered OT source at (RA, Dec) = 18h 30m 07.03s +76d 43m 13.3s on 2013-02-25.72934 UT. The OT unfiltered magnitude is 15.9m (limit 17.4m). The OT is seen in 4 images. There is no minor planet at this place. We have reference image without OT on 2012-08-21.59881 UT with unfiltered magnitude limit 19.2m.

There is a faint blue star near the OT position on digitized Palomar plates with a proper motion between two POSS epochs. It is listed is USNO catalogue as USNO-B1.0 1667-0088879 (18 30 07.213 +76 43 14.40 pmRA=2 pmDE=14 B1=20.73 R1=N/A B2=20.27 R2=20.15 I=N/A). The object is not present in 1RXS, GALEX, 2MASS, GCVS catalogs, as well as in AAVSO VSX. This area of sky is not covered by SDSS, CRTS and Palomar/NEAT.

Based on the amplitude of variability, blue color and proper motion on DSS plates we conclude that MASTER OT J183007.03+764313.3 is a new cataclysmic variable (dwarf nova) in outburst.

Follow up observations are required. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/183007.03764313.3.png

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