[vsnet-grb-info 17106] GRB 150921A: MASTER-NET bright OT detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18427
SUBJECT: GRB 150921A: MASTER-NET bright OT detection
DATE:    15/10/21 06:46:01 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov at xray.sai.msu.ru>

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

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

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

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

V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov
Blagoveschensk Educational State University, Blagoveschensk


V.Krushinski, I.Zalozhnih,  A. Popov
Ural Federal University, Kourovka

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

Claudio Mallamaci, Carlos Lopez and Federico Podest
Observatorio Astronomico Felix Aguilar (OAFA)



MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in SAAO was pointed to the  GRB151021A 25 sec after notice time 
and 50 sec after trigger time at 2015-10-21 01:30:06 UT in two 
polarizations. On our first (10s exposure)  set we  found 1 optical 
transient within SWIFT error-box (Melandri et. al GCN 18425) brighter then 
16.


date       time      Tmid-T0      Coord2000                       Mag
2015-10-21 01:30:06   55.0   (22h 30m 34.42s , -33d 11m 50.3s)    14.86

The 5-sigma upper limit has been about 16.0 mag
The message may be cited.