[vsnet-alert 15507] MASTER OT J212444.87+321738.3 - new very bright variable

[Taichi Kato]

   Wouldn't it be a nova like V407 Cyg?

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ATEL #4888							     ATEL #4888

Title:	Very bright OT detected by MASTER
Author:	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)
Queries:	lipunov2007 at gmail.com
Posted:	14 Mar 2013; 14:50 UT
Subjects:Infra-Red, Star, Transient, Variables

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 

<center><a href="http://observ.pereplet.ru/MASTER_OT.html">List of optical
transients discovered by MASTER</a></center>

Global MASTER Robotic Net: http://observ.pereplet.ru
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