GCN Circular 23576

V. Lipunov, N.Tiurina, E. Gorbovskoy, V.Kornilov,  P.Balanutsa,
A.Kuznetsov, D. Vlasenko, D.Kobtsev
(Lomonosov Moscow State University, SAI),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar),

H. Levato
(Instituto de Ciencias Astronomicas, de la Tierra y del Espacio of San 
Juan National University, Argentina)

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
(The Instituto de Astrofisica de Canarias),

D. Buckley (South African Astronomical Observatory),

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

O. Gress, N.M. Budnev, S. Yazev, O. Chuvalaev (Irkutsk State University, API)

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


MASTER-OAFA robotic telescope (Global MASTER Net  http://observ.pereplet.ru, 
Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in 
Argentina (OAFA observatory of San Juan National University) was pointed to the 
GRB181228A (Moss et al., GCN #23570) 26 sec after notice time and 47 sec after 
trigger time at 2018-12-28 02:54:05 UT. On our first (10s exposure)  set we 
found 1 optical transient within SWIFT XRT error-box  (Beardmore et al., GCN 
#23574) brighter than 17.5.


  T-Tmid      Date      Time     Expt.        Ra                Dec    Mag
    s                   UTC       s 
---------|-------------------|------|-----------------|-----------------|-------
     52   2018-12-28 02:54:05     10  ( 03h 19m 14.80s , +13d 12' 02".80 ) 17.0

The 5-sigma upper limit has been about 17.5 mag . Coordinate error ~2".

The galactic latitude b = -35 deg., longitude l = 170 deg.
The observations made on zenit distance = 49 deg.The moon (64 % bright part) 
below the horizon (The altitude of the Moon is -14 deg. ).
The sun  altitude  is -29.6 deg.
The object can be observed till 2018-12-28 06:59:09
The message may be cited.