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GCN Circular 18613

Subject
GRB GRB 151118A: MASTER-NET optical observations
Date
2015-11-18T11:11:38Z (8 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
V. Lipunov, E.Gorbovskoy, N.Tyurina, V.Kornilov, P.Balanutsa,
A.Kuznetsov, D. Vlasenko, D.Kuvshinov
Lomonosov Moscow State University, Sternberg Astronomical Institute

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

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

MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in Kislovodsk was pointed to the  GRB151118.13 30 sec after notice 
time and 44 sec after trigger time at 2015-11-18 03:07:17 UT. On our first 
(10s exposure)  set we haven`t found optical transient  within SWIFT 
error-box (ra=03 48 37 dec=+65 52 06 r=0.05).
The 5-sigma upper limit has been about 16.5  mag unfiltered.

MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in IAC was pointed to the  GRB151118A  24 sec after notice time 
and 42 sec after trigger time at 2015-11-18 03:07:12 UT in two 
polarizations. On our first (10s exposure)  set we haven`t found optical 
transient  within SWIFT error-box (Amaral-Rogers et al GCN 18611Not found
 
 
).
Our early upper limits on single and coadd images given in a table below:

Table 1.
5 sigma limit.

T-Ts  T-Tm  Expt.    P|     P-    coadd.
                     lim     lim 
----------------------------------------
   42    47    10    16.7   16.8     1
   42    90    50    17.9   18.0     3
   42   508   790    19.9   20.0    12
   86    96    20    17.3   17.4     1
  117   127    20    17.3   17.4     1
  147   218   120    18.7   18.8     3
  299   420   220    19.2   19.3     3
  551   762   400    19.6   19.7     3
---------------------------------------

  T   - is a trigger time [s].
Ts   - image start time [s].
Tm   - image middle time [s].
Expt - exposure time [s].
P|   - image upper limit in polarizer orientated 90 deg. to RA axis [mag].
P-   - image upper limit in polarizer orientated  0 deg. to RA axis [mag].

We do not see OT brighter 20 mag. There is marginal object (m~20) with 6" 
W (RA) and 3"S (dec)  offset from XRT error box center (Ra = 03h 48m 
40.40s Dec= 65d 54m 01.3s Mag ~ 20.3 +- 0.7  ).

The message may be cited.