Flare Star and new CV detected by MASTER

ATel #6011; S. Shurpakov, P. Balanutsa, D. Denisenko, V. Lipunov, E. Gorbovskoy, N. Tiurina, V. Kornilov, N. Shatskiy, V. Chazov, A. Kuznetsov, V. Vladimirov, V. Yecheistov (Moscow State University, SAI), V. Yurkov, Y. Sergienko, D. Varda, E. Sinyakov, A. Gabovich (Blagoveshchensk Educational University), K. Ivanov, S. Yazev, N. Budnev, E. Konstantinov, O. Chuvalaev, V. Poleshchuk, O. Gress (Irkutsk State University), A. Parkhomenko, A. Tlatov, D. Dormidontov, V. Senik (Kislovodsk Solar Station of Pulkovo Observatory), V. Krushinsky, I. Zalozhnih, A. Popov, A. Bourdanov (Ural Federal University), P. Podvorotny, V. Shumkov (MASTER team members), H. Levato, C. Saffe (ICATE), C. Mallamaci, C. Lopez, F. Podest (OAFA)
on 25 Mar 2014; 20:41 UT
Credential Certification: Nataly Tyurina (tiurina@sai.msu.ru)

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MASTER OT J181536.93+481627.9 - possible flare star of UV Ceti type

MASTER-Amur auto-detection system discovered OT source at (RA, Dec) = 18h 15m 36.93s +48d 16m 27.9s on 2014-03-24.82569 UT. The OT unfiltered magnitude is 17.6m (limit 18.5m). The OT is seen in 2 images. There is no minor planet at this place. We have reference image without OT on 2011-06-12.67756 UT with unfiltered magnitude limit 19.5m. The object was not detected on the first triplet of images taken 45 minutes before (at 18:59:30 UT, or on 2014-03-24.792 UT) to the limiting magnitude 18.3 and on the 60-sec exposure starting at 19:45:45 UT. It appears first on the image taken at 19:47:22 UT (17.9m) and brightens to 17.6m on the next image at 19:49:00 UT.

The OT at quiescence is identical to the infrared object AllWISE J181536.92+481629.7 (W1=16.78+/-0.06 W2=17.02+/-0.23). There is nothing at this position on digitized Palomar plates (m_lim~21), in GALEX, USNO, GSC, 2MASS, GCVS and AAVSO VSX. However, the faint object is visible on 2MASS infrared images obtained on 2000-06-21 at the following position: 18 15 36.97 +48 16 30.4 (astrometric error 0.2" in both coordinates). Comparison of the color-combined Palomar and 2MASS JHK images is uploaded to http://master.sai.msu.ru/static/OT/J181536+481627-BRIR-JHK.jpg (6'x6' FOV).

We also note the presence of a faint ROSAT X-ray source formally 31" from the OT: 1RXS J181538.9+481604 (position error 14", flux 0.0119+/-0.0042 counts/s, hardness ratios HR1=0.36+/-0.38 and HR2=-0.27+/-0.33). The X-ray source can be a combination of the flux from the flaring star and the irregular galaxy 2MASX J18154539+4815491 = GALEX J181545.5+481548.

Based on the amplitude and fast rise, MASTER OT J181536.93+481627.9 is most likely a flaring red dwarf. However, taking into account the possible relation to the X-ray source, follow up observations are encouraged. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/181536.93481627.9.png

MASTER OT J070027.31+552951.6 - new CV

MASTER-Tunka auto-detection system discovered OT source at (RA, Dec) = 07h 00m 27.31s +55d 29m 51.6s on 2014-03-25.53921 UT. The OT unfiltered magnitude is 17.4m (limit 19.6m). The OT is seen in 6 images. There is no minor planet at this place. We have reference image without OT on 2012-02-19.55348 UT with unfiltered magnitude limit 19.9m. The object has faded by 0.3m on the second triplet of images obtained an hour later (17.6m on 2014-03-25.585 UT).

The OT at quiescence is identical to the blue star USNO-B1.0 1454-0179160 (07 00 27.282 +55 29 51.51 B1=20.23 B2=21.00). Color-combined (BRIR) finder chart is uploaded to http://master.sai.msu.ru/static/OT/J070027+552951-BRIR5x5.jpg (2x zoom). There is nothing at this position in 1RXS, 2MASS, GCVS and AAVSO VSX. This area of sky in Lynx is not covered by GALEX, NEAT and SDSS. There are four previous outbursts to 18.0-18.5m in Catalina Sky Survey data.

Based on the blue color and amplitude of variability (~4m), MASTER OT J070027.31+552951.6 is a cataclysmic variable (dwarf nova in outburst). Follow up observations are encouraged. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/070027.31552951.6.png

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