TITLE: GCN CIRCULAR NUMBER: 33596 SUBJECT: Swift GRB 230409B: Global MASTER-Net observations report DATE: 23/04/09 16:58:40 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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 230409B ( A. P. Beardmore et al., GCN 33592) errorbox 42781 sec after notice time and 42806 sec after trigger time at 2023-04-09 16:50:23 UT, with upper limit up to 15.5 mag. Observations started at twilight. The observations began at zenith distance = 83 deg. The sun altitude is -12.2 deg. The galactic latitude b = -2 deg., longitude l = 99 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2209455 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 42897 | MASTER-Kislovodsk | C | 180 | 15.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited.