TITLE: GCN CIRCULAR NUMBER: 26074 SUBJECT: GRB 191023A: MASTER optical observation DATE: 19/10/25 17:37:47 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina,P.Balanutsa,A.Kuznetsov, V.Vladimirov, D. Vlasenko, I.Gorbunov,D.Zimnukhov,V.Senik, T.Pogrosheva, K.Pozdnyakov,A.Chasovnikov, V.Topolev,D.Kuvshinov(Lomonosov Moscow State University, SAI,Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile(Observatorio AstronomicoFelixAguilar 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 Global Robotic Net (http://observ.pereplet.ru, Lipunov etal.,2010,Advances in Astronomy, vol.2010, 30L) started Fermi GRB 191023A / trigger 593536021 (GBM team GCN 26060, BALROG team Biltzinger et al. GCN 26061) error box optical observation 596 sec after notice time (643 sec after trigger time) at 2019-10-23 15:17:40 UT. Real time updated cover map is available here: https://master.sai.msu.ru/site/master2/observ.php?id=1175192 MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the FERMI GRB191023.63 errorbox 596 sec after notice time (643 sec after trigger time) at 2019-10-23 15:17:40 UT, with upper limit up to 19.0 mag. Observations started at twilight. The observations began at zenith distance = 37 deg. The sun altitude was -11.8 deg. MASTER-Tavrida robotic telescope located in Russia started inspect of the FERMI GRB191023.63 errorbox 1974 sec after notice time (2021 sec after trigger time at 2019-10-23 15:40:37 UT), with upper limit up to 18.4 mag. Observations started at twilight. The observations began at zenith distance = 37 deg. The sun altitude was -10.2 deg. MASTER-Tunka robotic telescope located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the FERMI GRB191023.63 errorbox 1974 sec after notice time (80330 sec after trigger time at 2019-10-24 13:25:47 UT), with upper limit up to 18.0 mag. The observations began at zenith distance = 56 deg. The sun altitude was -32.8 deg. MASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) started inspect of the FERMI GRB191023.63 errorbox 1974 sec after notice time and 1 days 9459 sec after trigger time at 2019-10-24 17:44:36 UT, with upper limit up to 16.4 mag. Observations started at twilight. The observations began at zenith distance = 46 deg. The sun altitude is -10.4 deg. MASTER-IAC robotic telescope located in Spain (IAC Teide Observatory) started inspect of the FERMI GRB191023.63 errorbox 1974 sec after notice time (1 days 14406 sec after trigger time) at 2019-10-24 19:07:03 UT, with upper limit up to 17.9 mag. Observations started at twilight. The observations began at zenith distance = 24 deg. The sun altitude is -9.8 deg. MASTER-OAFA robotic telescope located in Argentina (OAFA observatory of San Juan National University) started inspect of the FERMI GRB191023.63 errorbox 1974 sec after notice time (1 days 30856 sec after trigger time at 2019-10-24 23:41:13 UT), with upper limit up to 17.3 mag. Observations started at twilight. The observations began at zenith distance = 47 deg. The sun altitude is -10.9 deg. MASTER-Amur robotic telescope located in Russia (Blagoveshchensk State Pedagogical University) started inspect of the FERMI GRB191023.63 errorbox 1974 sec after notice time (1 days 76356 sec after trigger time at 2019-10-25 12:19:32 UT), with upper limit up to 16.9 mag. The observations began at zenith distance = 62 deg. The sun altitude is -37.8 deg. The galactic latitude b = -60 deg., longitude l = 98 deg. Reduction will be continued, up to now there is no OT detected inside both error-boxes. The message may be cited.