TITLE: GCN CIRCULAR NUMBER: 31308 SUBJECT: Swift GRB 211225B: Global MASTER-Net observations report DATE: 21/12/26 06:56:11 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), B.L.Carrasco, J.R.Valdes,V.Chavushyan, C.J.Martinez, V.M.Patino Alvarez, M.L.H.Rodriguez (INAOE, OAGH) 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 211225B ( K. L. Page et al., GCN 31305) errorbox 50155 sec after notice time and 50206 sec after trigger time at 2021-12-26 03:09:05 UT, with upper limit up to 16.5 mag. Observations started at twilight. The observations began at zenith distance = 67 deg. The sun altitude is -16.1 deg. The galactic latitude b = 28 deg., longitude l = 39 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1826927 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 50296 | MASTER-Kislovodsk | C | 180 | 16.5 | 50296 | MASTER-Kislovodsk | C | 180 | 15.5 | 51607 | MASTER-Kislovodsk | C | 180 | 13.3 | 51607 | MASTER-Kislovodsk | C | 180 | 13.2 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.