TITLE: GCN CIRCULAR NUMBER: 45651 SUBJECT: IceCube Alert 260919A: Global MASTER-Net observations report DATE: 26/09/20 02:40:02 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya..Kechin, V.Senik, A.Chasovnikov, K.Labsina (Lomonosov MSU) D.Buckley (SAAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) A.Sosnovskij (Lomonosov MSU) A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory) L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) R.Rebolo (The Instituto de Astrofisica de Canarias) O.Gress, N.Budnev(ISU) M. Segura, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA) MASTER-Tavrida robotic telescope [1] located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the IceCube Alert 260919A (trigger No 38400235,07h 24m 12.00s , +06d 25m 48.0s, R=0.27) errorbox 68090 sec after notice time and 68168 sec after trigger time at 2026-09-20 01:48:23 UT, with upper limit up to 18.1 mag. The observations began at zenith distance = 58 deg. The sun altitude is -17.8 deg. The galactic latitude b = 11 deg., longitude l = 211 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3507256 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 68198 | 2026-09-20 01:48:23 | MASTER-Tavrida | (07h 23m 51.02s , +06d 36m 35.9s) | C | 60 | 18.0 | 68198 | 2026-09-20 01:48:24 | MASTER-Tavrida | (07h 23m 53.02s , +06d 35m 24.8s) | C | 60 | 17.9 | 68272 | 2026-09-20 01:49:37 | MASTER-Tavrida | (07h 23m 58.11s , +06d 35m 32.5s) | C | 60 | 16.6 | 68294 | 2026-09-20 01:49:59 | MASTER-Tavrida | (07h 23m 52.57s , +06d 33m 19.5s) | C | 60 | 17.7 | 68345 | 2026-09-20 01:50:50 | MASTER-Tavrida | (07h 23m 56.88s , +06d 34m 31.6s) | C | 60 | 18.1 | 68981 | 2026-09-20 02:01:26 | MASTER-Tavrida | (07h 23m 54.95s , +06d 35m 32.0s) | C | 60 | 16.2 | 68981 | 2026-09-20 02:01:26 | MASTER-Tavrida | (07h 23m 56.54s , +06d 34m 23.9s) | C | 60 | 16.3 | 69053 | 2026-09-20 02:02:38 | MASTER-Tavrida | (07h 23m 54.98s , +06d 34m 08.3s) | C | 60 | 14.3 | 69076 | 2026-09-20 02:03:01 | MASTER-Tavrida | (07h 24m 00.30s , +06d 34m 32.5s) | C | 60 | 14.3 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html