GCN Circular 21147

R.Podesta, C.Lopez, F. Podesta Observatorio Astronomico Felix Aguilar (OAFA),
National University of San Juan, Argentina

H. Levato, C. Saffe
Instituto de Ciencias Astronomicas,de la Tierra y del Espacio (ICATE),
San Juan, Argentina

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, D.Kuvshinov, A.V.Krylov,
I.Gorbunov, P.Balanutsa, A.Kuznetsov, V.V.Chazov, D. Vlasenko
Lomonosov Moscow State University, Sternberg Astronomical Institut of MSU

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

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

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

D.Buckley, S. Potter, A.Kniazev, M.Kotze
South African Astronomical Observatory

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias


MASTER   robotic telescope (6 square degrees) 
located in OAFA was pointed to the  GRB170525B (Barthelmy et al., GCN 
#21142) 15191 sec after notice 
time and 43294 sec after trigger time at 2017-05-25 22:42:14 UT. On our 
first (180s exposure)  set we haven`t found optical transient  within 
Master error-box (ra=90.8625 dec=-17.0861 r=0.1).

The 5-sigma upper limit has been about 18.3 mag

There is no OT at added images brighter 19.9 at Swift XRT position 
(Barthelmy et al., GCN #21142; Evans, GCN #21144 ).

The observations made on zenit distance = 59 degrees, galaxy latitude b = 
-18 degree.
The moon ( 0 % bright part) below the horizon (The altitude of the Moon is 
-8 degree ).
Observations started at twilight. The sun  altitude  is -12.7 degree.
The object can be observed till 2017-05-26 01:12:20

The message may be cited.