TITLE: GCN CIRCULAR NUMBER: 26514 SUBJECT: Swift GRB191220.56: Global MASTER-Net observations report DATE: 19/12/20 13:46:43 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov, D. Cheryasov (Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), H.Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University) MASTER-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the Swift GRB191220.56 (trigger No 945344,18h 45m 33.79s , +26d 40m 01.9s, R=0.05) errorbox 13 sec after notice time and 90 sec after trigger time at 2019-12-20 13:31:08 UT, with upper limit up to 16.0 mag. The observations began at zenith distance = 82 deg. The sun altitude is -40.9 deg. The galactic latitude b = 13 deg., longitude l = 57 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1233370 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 101 | MASTER-Tunka | P| | 20 | 14.9 | 140 | MASTER-Tunka | P| | 20 | 15.0 | 185 | MASTER-Tunka | P| | 30 | 15.5 | 239 | MASTER-Tunka | P| | 40 | 15.4 | 304 | MASTER-Tunka | P| | 50 | 15.8 | 383 | MASTER-Tunka | P| | 70 | 15.9 | 477 | MASTER-Tunka | P| | 80 | 16.0 | The observation and reduction will continue. The message may be cited.