TITLE: GCN CIRCULAR NUMBER: 23922 SUBJECT: IceCube-190221A: MASTER Global Robotic Net optical observation DATE: 19/02/21 20:50:22 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, N.Tyurina, V.Kornilov, D.Vlasenko, V.Vladimirov, D.Zimnukhov, A.Kuznetsov, P.Balanutsa, V.Senik, A. Chasovnikov, V.Topolev, D.Kuvshinov (Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C. Lopez, C.Francile, F. Podesta (Observatorio Astronomico Felix Aguilar OAFA), H.Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE) O. Gress, N.M. Budnev, O.Ershova, Yu.Ishmuhametova (Applied Physics Institute,Irkutsk State University), V. Yurkov, A. Gabovich, Yu. Sergienko, D. Kobcev (Blagoveschensk Educational State University), R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres (The Institutode Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the IC190221A (The IceCube Collaboration GCN 23918) 17 sec after notice time (47 sec after trigger time) at 2019-02-21 08:26:26 UT. The 5-sigma upper limit ~19 mag (180s exposition), we have 9 expositions. Also we have 4 images of the part of IC error-box in time ntervall 2019-02-21 08:01:49-08:14:20UT (11 minutes befor neutrino alert) during Fermi trigger inspection . The full analysys of ICECUBE error-box (RA: 268.81 [-1.8,+1.2], Dec: -17.04 [-0.5,+1.3] ) will be continued. The error box center galactic latitude b = 3.5 deg., longitude l = 11.7deg. The observations started when error-box altitude was 33deg. The sun altitude is -23.0 deg. The moon (96 % bright part) was 43 deg. above the horizon. The distance between moon and object was 91 The message may be cited.