TITLE: GCN CIRCULAR NUMBER: 31274 SUBJECT: Swift GRB 211221A: Global MASTER-Net observations report DATE: 21/12/22 00:56:25 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, E.Gorbovskoy, K.Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko, G.Antipov, D.Zimnukhov, V.Senik, T.Pogrosheva, E.Minkina, A.Chasovnikov, V.Topolev, V.Grinshpun, D.Kuvshinov, 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 (Blagoveschensk Educational State University) MASTER-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 211221A ( K. L. Page et al., GCN 31273) errorbox 3401 sec after notice time and 3560 sec after trigger time at 2021-12-21 21:48:01 UT, with upper limit up to 14.8 mag. The observations began at zenith distance = 46 deg. The sun altitude is -68.8 deg. MASTER-OAFA robotic telescope located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB 211221A errorbox 13726 sec after notice time and 13885 sec after trigger time at 2021-12-22 00:40:06 UT, with upper limit up to 16.7 mag. Observations started at twilight. The observations began at zenith distance = 54 deg. The sun altitude is -12.1 deg. The galactic latitude b = -20 deg., longitude l = 201 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1823335 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 3651 | MASTER-Kislovodsk | C | 180 | 12.7 | 3651 | MASTER-Kislovodsk | C | 180 | 12.2 | 3851 | MASTER-Kislovodsk | C | 180 | 13.0 | 3851 | MASTER-Kislovodsk | C | 180 | 13.4 | 4052 | MASTER-Kislovodsk | C | 180 | 14.2 | 4052 | MASTER-Kislovodsk | C | 180 | 14.2 | 4252 | MASTER-Kislovodsk | C | 180 | 14.8 | 4252 | MASTER-Kislovodsk | C | 180 | 14.5 | 4453 | MASTER-Kislovodsk | C | 180 | 14.4 | 4453 | MASTER-Kislovodsk | C | 180 | 13.5 | 10415 | MASTER-Kislovodsk | C | 180 | 14.5 | 10896 | MASTER-Kislovodsk | C | 180 | 13.8 | 10896 | MASTER-Kislovodsk | C | 180 | 14.4 | 11497 | MASTER-Kislovodsk | C | 180 | 13.4 | 11497 | MASTER-Kislovodsk | C | 180 | 13.1 | 11897 | MASTER-Kislovodsk | C | 180 | 13.5 | 12787 | MASTER-Kislovodsk | C | 180 | 14.1 | 12787 | MASTER-Kislovodsk | C | 180 | 14.1 | 13976 | MASTER-OAFA | C | 180 | 16.7 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.