Very bright OT detected by MASTER

ATel #4888; N. Tiurina, V. Lipunov, E. Gorbovskoy, D. Denisenko, P. Balanutsa, V. Kornilov, A. Belinski, N. Shatskiy, V. Chazov, A. Kuznetsov, V. Yecheistov, 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 14 Mar 2013; 14:50 UT
Credential Certification: Vladimir Lipunov (lipunov2007@gmail.com)

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MASTER OT J212444.87+321738.3 - new very bright variable

MASTER-Amur auto-detection system discovered OT source at (RA, Dec) = 21h 24m 44.87s +32d 17m 38.3s on 2013-03-13.84134 UT. The OT unfiltered magnitude is 10.7m (limit 16.9m). The OT is seen in 6 images. There is no minor planet at this place. We have reference image with OT at 13.5m on 2012-10-21.52326 UT (magnitude limit 18.5m). The object is close to saturation on Mar. 13 images, so the real magnitude may be yet brighter.

There is nothing at this position in GCVS and AAVSO VSX. No variability was detected by NSVS (ROTSE-I) project. The object is identical to USNO-B1.0 1222-0647260 (21 24 45.007 +32 17 38.09 B1=18.78 R1=14.96 B2=20.88 R2=16.32 I=13.14), 2MASS 21244500+3217377 (J=7.82+/-0.03 H=5.97+/-0.02 K=4.82+/-0.02) and WISE J212444.98+321737.73.440 (W1=3.44+/-0.13 W2=2.21+/-0.10 W3=-0.43+/-0.03 W4=-1.28+/-0.01). This area of sky in Cygnus is not covered by CRTS and GALEX.

The galactic reddening in this direction is A_R=0.55, A_V=0.68 (from Schlegel et al., 1998) or A_R=0.45, A_V=0.57 (from Schlafly et al., 2011). Color-combined (BRIR) finder chart is posted at http://master.sai.msu.ru/static/OT/J212444+321738-BRIR.jpg (10'x10' FOV).

Based on the large (J-K) color index of 3.0 we suggest that MASTER OT J212444.87+321738.3 is a new large amplitude variable of C or S spectral type. Follow up observations are required. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/212444.87321738.3.png

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