[vsnet-grb-info 20332] GRB180221A: MASTER-OAFA optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22428
SUBJECT: GRB180221A: MASTER-OAFA optical observations
DATE:    18/02/21 07:57:28 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov at xray.sai.msu.ru>

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

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),

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

R. Rebolo, M. Serra
(The Instituto de Astrofisica de Canarias),

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

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

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


MASTER-OAFA  robotic telescope (MASTER-Net: http://observ.pereplet.ru) located 
in Argentina was pointed to the Swift possible GRB 180221A (Stamatikos et al GCN 22427)
  119 sec after notice time and 257 sec after trigger time at 2018-02-21 06:35:01 UT.
On our first (50s exposure)  set we didn't find optical transient  within 
SWIFT-BAT error-box (RA, Dec 326.772, -72.868, radius 3arcmin).

The 5-sigma upper limit has been about 18.3  mag at single (50 sec) and 
19.5  at coadd (310 sec) images.

The message may be cited.

====================================================================
The observations were made on
zenit distance 73 degrees,
The Sun  altitude  is -40.6 degree.
Dist. to Moon: 92.17 (Moon coord. 35.522966 d, 8.630816 d)