TITLE: GCN CIRCULAR NUMBER: 33602 SUBJECT: Fermi GRB 230409C: Global MASTER-Net observations report DATE: 23/04/09 23:30:34 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) started inspect of the Fermi GRB 230409C ( Fermi GBM team, GCN 33600) errorbox 730 sec after notice time and 764 sec after trigger time at 2023-04-09 22:40:30 UT, with upper limit up to 18.5 mag. The observations began at zenith distance = 20 deg. The sun altitude is -65.6 deg. The galactic latitude b = 9 deg., longitude l = 305 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2209581 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 795 | 2023-04-09 22:40:30 | MASTER-SAAO | (13h 00m 51.38s , -51d 57m 13.0s) | C | 60 | 18.5 | 795 | 2023-04-09 22:40:30 | MASTER-SAAO | (13h 02m 19.20s , -51d 57m 32.2s) | C | 60 | 18.1 | 874 | 2023-04-09 22:41:49 | MASTER-SAAO | (13h 13m 56.04s , -51d 57m 33.2s) | C | 60 | 18.5 | 874 | 2023-04-09 22:41:49 | MASTER-SAAO | (13h 15m 24.08s , -51d 57m 53.0s) | C | 60 | 18.2 | 965 | 2023-04-09 22:43:20 | MASTER-SAAO | (12h 46m 05.45s , -53d 51m 04.3s) | C | 60 | 18.1 | 965 | 2023-04-09 22:43:20 | MASTER-SAAO | (12h 44m 33.80s , -53d 50m 45.9s) | C | 60 | 18.4 | 1055 | 2023-04-09 22:44:50 | MASTER-SAAO | (12h 58m 02.95s , -53d 49m 21.9s) | C | 60 | 18.3 | 1055 | 2023-04-09 22:44:50 | MASTER-SAAO | (12h 59m 34.54s , -53d 49m 40.0s) | C | 60 | 18.0 | 1135 | 2023-04-09 22:46:10 | MASTER-SAAO | (12h 36m 21.97s , -51d 54m 36.6s) | C | 60 | 18.5 | 1135 | 2023-04-09 22:46:10 | MASTER-SAAO | (12h 37m 49.51s , -51d 54m 53.1s) | C | 60 | 18.1 | 1225 | 2023-04-09 22:47:40 | MASTER-SAAO | (12h 49m 21.46s , -51d 55m 58.1s) | C | 60 | 18.5 | 1225 | 2023-04-09 22:47:40 | MASTER-SAAO | (12h 50m 49.05s , -51d 56m 14.7s) | C | 60 | 18.0 | 1305 | 2023-04-09 22:49:00 | MASTER-SAAO | (12h 53m 17.46s , -50d 02m 47.1s) | C | 60 | 18.5 | 1305 | 2023-04-09 22:49:00 | MASTER-SAAO | (12h 54m 41.67s , -50d 03m 03.6s) | C | 60 | 18.1 | 1608 | 2023-04-09 22:54:03 | MASTER-SAAO | (13h 05m 37.80s , -50d 02m 55.9s) | C | 60 | 18.5 | 1608 | 2023-04-09 22:54:03 | MASTER-SAAO | (13h 07m 02.06s , -50d 03m 17.0s) | C | 60 | 18.1 | 1698 | 2023-04-09 22:55:33 | MASTER-SAAO | (12h 54m 22.04s , -55d 43m 47.0s) | C | 60 | 18.3 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.