TITLE: GCN CIRCULAR NUMBER: 34281 SUBJECT: Swift GRB230728.12: Global MASTER-Net observations report DATE: 23/07/28 02:56:43 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, E.Gorbovskoy, K.Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko, G.Antipov, D.Zimnukhov, V.Senik, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D.Cheryasov, Ya.Kechin (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 (Irkutsk State University, API), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (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 Swift GRB230728.12 (trigger No 1181187,22h 54m 09.36s , +28d 09m 03.6s, R=0.05) errorbox 19 sec after notice time and 36 sec after trigger time at 2023-07-28 02:50:40 UT, with upper limit up to 17.2 mag. The observations began at zenith distance = 64 deg. The sun altitude is -33.9 deg. The galactic latitude b = -28 deg., longitude l = 94 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2246027 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 42 | MASTER-SAAO | P/ | 10 | 16.3 | 42 | MASTER-SAAO | C | 10 | 17.2 | 61 | MASTER-SAAO | P/ | 10 | 16.4 | 61 | MASTER-SAAO | C | 10 | 17.2 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.