GCN Circular 12021

V.Krushinski, I.Zalozhnich, A. Popov
Ural State University, Kourovka

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

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

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

V.Yurkov, Yu.Sergienko, I.Kudelina
Blagoveschensk Educational State University, Blagoveschensk

  MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in Ural(Kaurovka) was pointed to the  GRB110520A 53 sec after 
GRB time and 23 sec after the trigger  at 2011-05-20 20:29:41.097 UT.
On our first (10s exposure) set we  haven`t found optical transient 
within SWIFT error-box (ra=08 57 31 dec=+56 23 59 r=0.050000).
The our unfilterd 5-sigma upper limit has been about 17.0 mag

  MASTER II  robotic telescope in Tunka(Siberia) also pointed to this GRB, 
28 sec after trigger time in two polarizations. But the Sun was too high
  (only 5 deg. below horizont) and upper limit is about 15.0 mag on the 
bosh  first 10 sec sets.

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