[vsnet-grb-info 27004] GRB 201221C: MASTER optical observtion

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29107
SUBJECT: GRB 201221C: MASTER optical observtion
DATE:    20/12/21 19:41:01 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov at xray.sai.msu.ru>

V. Lipunov, V.Kornilov, E.Gorbovskoy, N.Tiurina, P.Balanutsa,A.Kuznetsov,K.Zhirkov, F.Balakin,
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, A.Chasovnikov,A.Pozdnyakov,
V.Topolev, D.Cheryasov(Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev (Irkutsk State University, API),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov, Yu. Sergienko (Blagoveschensk Educational State University)

MASTER-IAC robotic telescope (Global MASTER-Net:  http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, 
vol. 2010, 30L) located in Spain (IAC Teide Observatory) was pointed to 
the  GRB201221.78 133 sec after notice time and 208 sec after trigger time 
at 2020-12-21 18:45:02 UT. On our 11-th (180s exposure)  set , obtained 
1451 sec after tigger time at 2020-12-21 19:05:45 UT, we haven`t found 
optical transient  within Swift error-box (ra=278.204 dec=34.4108 r=0.05).
The 5-sigma upper limit has been about  13.6mag
The message may be cited.

The galactic latitude b = 18 deg., longitude l = 63 deg.
The observations made on zenith distance = 69 deg.The moon (48 % bright 
part) is 56 deg. above the horizon. The distance between  moon and  object 
is 87
  Observations started at twilight.
The sun  altitude  is -11.4 deg.
The object can be observed till sunrise at 2020-12-22 07:52:15 
The 5-sigma upper limit has been about  14.9mag The message may be cited.