[vsnet-grb-info 16497] GRB 150428A: MASTER-net early optical observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17778
SUBJECT: GRB 150428A: MASTER-net early optical observation 
DATE:    15/04/28 15:19:00 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov at xray.sai.msu.ru>

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

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

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  GRB150428A (Page et al, GCN 17765) 28 
sec after notice time and 90 sec after trigger time at 2015-04-28 01:32:10 
UT in two polarizations. On our first  single and coadd images  we haven`t 
found optical transient  within SWIFT error-box . The observations made on 
a high zenith distance  ~ 80 d.
We obtain a followin upper limits:



Date start  T_s-T_tr   T_m-T_trig     Expt.  Limit Coadd
                       (mean_time)
01:32:10.9    90          100          20      16.0   no
01:32:43.2   122          132          20      16.0   no
01:33:14.7   153          168          30      16.4   no
01:33:14.7   153          224         120      17.0    3
01:33:14.7   153          583         770      18.5    9

Also, we can not confirm  Danish 1.56m OT (Andersen et. al GCN 17771), 
because they do not see it on our images with upper limits specified 
above.


The message may be cited.