GCN Circular 13285

E. Gorbovskoy, V. Lipunov, V.Kornilov, D.Kuvshinov, D.Denisenko, A.Belinski,
N.Tyurina, N.Shatskiy, P.Balanutsa, D.Zimnukhov, A.Kuznetsov,  V.V.Chazov, 
A.Kuznetsov
Moscow Lomonosov State University, Sternberg Astronomical Institute,

A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik
Kislovodsk Solar Station of the Pulkovo Observatory

K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk
Irkutsk State University

V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov
Blagoveschensk Educational State University, Blagoveschensk

V.Krushinski, I.Zalozhnich,  A. Popov, A. Bourdanov, A. Punanova
Ural Federal University

Hugo Levato and Carlos Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

Claudio Mallamaci, Carlos Lopez and Federico Podest
Observatorio Astronomico Felix Aguilar (OAFA)

MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in Kislovodsk was pointed to the Fermi Trigger 
358364818/GRB120510B 36 sec after GRB 
time at 2012-05-10 17:47:32.938 UT. On our Very Wide Field Camera 
(400 square degrees, 1 pix = 22 arcsec) set of images we 
have found optical transient within FERMI error-box with ~10 mag 
(unfiltered).

The OT position is:
Ra  =  12h 51m 37.9s
Dec = +00d 05m 35s
with the error box (one sigma) radius equal to 10".

We have reference image without OT on 2012-04-21 20:11:39 UT with 
unfiltered magnitude limit 12.5 m. 
In the follow up MASTER II Amur observations on 2012-05-11 at 15:12:29 UT 
there is no OT brighter than 17.2 m.
There are  two SDSS galaxies  inside one sigma error box:
SDSS J125138.22+000534.5 (rmag=19.83) and
SDSS J125138.45+000534.7 (rmag=21.98)
The data reduction is continuing.


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