Two Optical Transients detected by MASTER

ATel #5853; V. Shumkov, 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), 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. Yurkov, Y. Sergienko, D. Varda, E. Sinyakov, A. Gabovich (Blagoveshchensk Educational University), V. Krushinsky, I. Zalozhnih, A. Popov, A. Bourdanov (Ural Federal University), P. Podvorotny, S. Shurpakov (MASTER team members), H. Levato, C. Saffe (ICATE), C. Mallamaci, C. Lopez, F. Podest (OAFA)
on 5 Feb 2014; 12:51 UT
Credential Certification: Vladimir Lipunov (lipunov2007@gmail.com)

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MASTER OT J121800.71+502112.8 - new CV?

MASTER-Tunka auto-detection system discovered OT source at (RA, Dec) = 12h 18m 00.71s +50d 21m 12.8s on 2014-02-03.67354 UT. The OT unfiltered magnitude is 19.3m (limit 19.9m). The OT is seen in 4 images. There is no minor planet at this place. We have reference image without OT on 2013-05-15.648 UT with unfiltered magnitude limit 19.6m.

There is nothing at this position in any catalogs. The nearest object in SDSS is 11" away (a galaxy with r=19.3 which is probably unrelated to the OT). However, there is a faint object (~23.5m) marginally visible on the SDSS color-combined image.

Based on the outburst amplitude (more than 4m), MASTER OT J121800.71+502112.8 is most likely a cataclysmic variable (dwarf nova in outburst). Spectral observations are required. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/121800.71502112.8.jpg

MASTER OT J183521.81+442235.8 - flare star in Kepler field

MASTER-Tunka auto-detection system discovered OT source at (RA, Dec) = 18h 35m 21.81s +44d 22m 35.8s on 2014-02-04.87547 UT. The OT unfiltered magnitude is 16.4m (limit 18.1m). The OT is seen in 3 images. There is no minor planet at this place. We have reference image without OT on 2011-08-20.64162 UT with unfiltered magnitude limit 19.6m.

The OT was first detected on 60-sec unfiltered exposure starting at 20:58:38 UT as an object of 15.9m. It has faded to 16.4m on the next exposure at 21:00:41 UT and further to 16.9m at 21:02:52 UT. The object was not present on the second triplet of images obtained 45 minutes later starting at 21:45:33 UT (limiting magnitude 18.2).

The object at quiescence is identical to the red star USNO-B1.0 1343-0328027 (18 35 21.963 +44 22 35.54 R2=19.89 I=17.71) = 2MASS J18352194+4422356 (J=16.02+/-0.08 H=15.31+/-0.09 K=15.27+/-0.15). Color-combined DSS finder chart is uploaded to http://master.sai.msu.ru/static/OT/J183521+442235-BRIR5x5.jpg (2x zoom). There is nothing at this position in 1RXS, GCVS and AAVSO VSX. This area of sky in Lyra is not covered by SDSS. The object was included into Kepler Input Catalog as KIC 8340579.

Based on the fast fading and the red color, MASTER OT J183521.81+442235.8 is a new variable of UV Ceti type (flaring red dwarf). Follow up observations are encouraged. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/183521.81442235.8.png

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