GCN Circular 22444

V.Vladimirov, V. Lipunov, E.Gorbovskoy, N.Tyurina, V.Kornilov, 
D.Zimnukhov,   A.Krylov, I.Gorbunov, P.Balanutsa, A.Kuznetsov, V.Chazov, 
D. Kuvshinov (Lomonosov Moscow State University, SAI)

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

D.Buckley, S. Potter
(South African Astronomical Observatory),

O.Gres,  N.M.Budnev
(Irkutsk State University),

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

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),

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



MASTER-Kislovodsk (Russia)  robotic telescope (MASTER-Net: 
http://observ.pereplet.ru) located in Kislovodsk was pointed to
the  GRB180224.93 21 sec after  notice time and 37 sec after trigger time 
at 2018-02-24 22:21:44 UT. On our  unfiltered polarizing  exposures
set we  found 1 bright optical transient within  SWIFT
error-box (ra=202.658 dec=38.0878 r=0.05) 
brighter then 18.1.

RA,DEC  = 13h 30m 44.057s , +38d  04m 44.55 s
Error = 0.1 arcsec
maximal magnitute ~ 16.7


The 5-sigma upper limit has been about 18.1mag
The message may be cited.


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The observations made on zenit distance = 23 degrees, galaxy latitude b = 
76 degree.
The moon (68 % bright part) is 16 degrees above the horizon. The distance 
between  moon and  object is 97 degrees.
The sun  altitude  is -53.0 degree.
The object can be observed till sunrise at 2018-02-25 03:53:29 UT.


MASTER-SAAO  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in SAAO was pointed to the  GRB180224.94 92 sec after notice time 
and 176 sec after trigger time at 2018-02-24 22:24:12 UT. On our first
  set we  not found optical transient within SWIFT error-box 
(ra=202.638 dec=38.0819 r=0.1) brighter then 15.8.

The 5-sigma upper limit has been about 15.8 mag
The message may be cited.


The observations made on high zenit distance = 82 degrees, galaxy latitude 
b = 76 degree.
The moon (68 % bright part) is  6 degrees above the horizon. The distance 
between  moon and  object is 97
The sun  altitude  is -48.3 degree.
The object can be observed till sunrise at 2018-02-25 04:21:26.


This message can be cited.