TITLE: GCN CIRCULAR NUMBER: 30864 SUBJECT: IceCube Alert 210922.76: Global MASTER-Net observations report DATE: 21/09/23 03:13:21 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru> 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), 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the IceCube Alert 210922.76 (trigger No 30987826,04h 02m 55.20s , -04d 10m 48.0s, R=0.65) errorbox 30295 sec after notice time and 30428 sec after trigger time at 2021-09-23 02:44:29 UT, with upper limit up to 17.5 mag. The observations began at zenith distance = 28 deg. The sun altitude is -22.4 deg. The galactic latitude b = -38 deg., longitude l = 195 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1729682 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 30518 | 2021-09-23 02:44:29 | MASTER-SAAO | (04h 01m 54.27s , -04d 29m 17.4s) | C | 180 | 16.4 | 30661 | 2021-09-23 02:47:51 | MASTER-SAAO | (04h 00m 48.01s , -04d 38m 16.4s) | C | 60 | 17.4 | 30744 | 2021-09-23 02:49:15 | MASTER-SAAO | (04h 08m 46.41s , -04d 39m 25.3s) | C | 60 | 17.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.