GCN Circular 22797

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

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

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

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

H.Levato, C. Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

D. Buckley
South African Astronomical Observatory

O. Gres, N.M.Budnev , Yu.Ishmuhametova
Irkutsk State University

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

MASTER-Kislovodsk  robotic telescope (MASTER-Net: http://observ.pereplet.ru 
Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) ,
located in Kislovodsk Solar Station of Pulkovo observatory,
was pointed to the Swift GRB180618A (LaPorte et al. GCN #22790; Sakamoto 
et al., GCN #22796)
25 sec after notice time and 41 sec after trigger time at 2018-06-18 
00:43:53 UT.
On our first (10s exposure)  polarization set we haven`t found optical 
transient  within SWIFT error-box (ra=169.933 dec=73.8478 r=0.05).
The 5-sigma upper limit has been about 15.2 mag

The observations made on zenit distance = 61 degrees, galaxy latitude b = 
42 degree.
The moon (24 % bright part) below the horizon (The altitude of the Moon is 
-31 degree ).
Observations started at twilight and bad transparency.  The sun  altitude 
is -6.8 degree.

  MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in IAC was pointed to the  GRB180618A 1734  sec after trigger time 
at 2018-06-18 01:12:07 UT.
On our first (180s exposure)  set we found  ~19 mag optical transient 
within SWIFT UVOT error-box (LaPorte et al. GCN #22790; Guidorzi et al., 
GCN #22792;).
  The 5-sigma upper limit has been about 19.0 mag on single (180 s) and 
20.5 on coadd (1800 s) exposures.

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  The observations made on zenit distance = 64 degrees, galaxy latitude b = 
42 degree. 
The moon (24 % bright part) below the horizon (The altitude of the Moon is 
-15 degree ). 
The sun  altitude  is -38.3 degree. 
The object can be observed till sunrise at 2018-06-18 06:08:21 
The message may be cited.