TITLE:   GCN CIRCULAR
NUMBER:  21250
SUBJECT: GRB170612.87 MASTER-Net OT detection
DATE:    17/06/12 21:01:53 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

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

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

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

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

R. Podesta, Carlos Lopez and F. Podesta
Observatorio Astronomico Felix Aguilar (OAFA)

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

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

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

MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Crimea was pointed to the  GRB170612.87 87 sec after notice time and 162 sec after trigger time at 2017-06-12 20:57:53 UT. On our first (30s exposure)  set we  found 1 optical transient within SWIFT error-box (ra=262.729 dec=-5.97806 r=0.05) brighter then 16.9.


 T-Tmid      Date      Time       Expt.        Ra                Dec           Mag
---------|---------------------|-------|-----------------|-----------------|-------
     177   2017-06-12 20:57:53      30   ( 17h 31m 04.7s , - 5d 59m 39.2s)    15.25

The 5-sigma upper limit has been about 16.9mag
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