GCN Circular 20947

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

D.Buckley
South African Astronomical Observatory

R. Rebolo, M. Serra,
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


O.Gress, N.M.Budnev, K.Ivanov 
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


MASTER-SAAO  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in SAAO was pointed to the  Fermi trigger 512347439/GRB 
170327A (ra=18 26 16 dec=-33 27 00 r=5.3167)  2823 sec after notice time 
and 2870 sec after trigger time at 2017-03-27 23:31:45 UT in inspection 
mode.


MASTER-SAAO auto-detection system ( Lipunov et al., "MASTER Global Robotic  Net",
Advances in Astronomy, 2010, 30L ) discovered OT source
MASTER OT J184546.55-352847.6 
at (RA, Dec) = 18h 45m 46.55s -35d 28m 47.6s on 2017-03-28.06645 UT/

The OT's unfiltered magnitude is 17.0m (mlim=19.0).
There are only 2 images of this area (MASTER inspection mode) and OT is 
seen in both images on
Tstart=2017-03-28 01:35:41UT and
Tstart=2017-03-28 01:42:14UT with exposition duration 60s (each).

There is no minor planet at this place except (208700)_2002_JK with 
Vmag=20.4 and 0.6E,7.0S offset (doesn't have any connection with our OT).

We have reference image on 2016-05-14.93352 UT with unfiltered mlim= 
19.1m, the nearest in time images of this area are in MASTER-IAC database 
on 2016-07-31 23:23:26 with mlim=19.4.
There is no any sources in VIZIER database, it means 22mag limit in 
history

Deep photometry and Spectral observations are required.
The discovery and reference images are available at:
http://master.sai.msu.ru/static/OT/MASTEROTJ184546.55-352847.6.jpg


The observations made on zenit distance = 23.91 deg.
The distance to Moon was Dist. to Moon: 85.299167
The sun  altitude  was -58.18 degree.

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