TITLE:   GCN CIRCULAR
NUMBER:  20514
SUBJECT: GRB 170121B:  MASTER early optical observations of the Swift possible XT
DATE:    17/01/24 14:05:20 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

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

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

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

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

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

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 II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in 
Blagoveschensk was pointed to the  Fermi trigger Number 506702667 
(Hamburg et al., 20505)  72 sec 
after notice time and 171 sec after trigger time at 2017-01-21 14:47:14 UT.

MASTER-Amur auto-detection system discovered MASTER OT J045017.73-091602.0
with unfiltered magnitude is 14.9m (limit 16.0 m) (Lipunov et al., GCN 20502).

We do not see any optical source at Swift XRT position (Sbarufatti et 
al., GCN 20510) with next limits:

  Date         UT        Exp        Type        Limit
             start

2017-01-21 14:50:48 	60	Alert (FERMI)	16.6

2017-01-21 14:49:21     60	Alert (FERMI)	16.1

2017-01-21 14:48:11     40	Alert (FERMI)	16.4

2017-01-21 14:47:14     30	Alert (FERMI)	16.0

2017-01-21 14:46:28     20	Alert (FERMI)	16.0


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