TITLE:   GCN CIRCULAR
NUMBER:  21272
SUBJECT: GRB 170626A: MASTER-Tunka OT detection. 
DATE:    17/06/27 13:49:43 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

O.Gres, N.M.Budnev, O.Ershova
Irkutsk State University

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

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

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

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

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

MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in Tunka was starting inspection on the Swift  GRB 170626A 
error-box (ra=11 01 34 dec=+56 28 36 r=0.05)  22799 sec after notice time and 24464 
sec after trigger time at 2017-06-26 16:45:56 UT. The 5-sigma upper limit 
on our added image (3x180s exposure)  set is about 19.8  mag .

We see OT with unfiltered magnitude 19.8 +0.2/-0.3 mag at Moskvitin et 
al. (GCN #21268) position (see also A. de Ugarte Postigo et al.,GCN 
#21269; Melandri et al., GCN #21270; ).


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