TITLE: GCN CIRCULAR NUMBER: 35684 SUBJECT: GRB 240205B: MASTER OT J232550.14-550704.6 counterpart detection DATE: 24/02/05 23:02:28 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V.Lipunov, Ya.Kechin, N.Tiurina, G.Antipov E.Gorbovskoy (Lomonosov MSU), D.Buckley (SAAO), D.Svinkin (Ioffe Institute, Konus-Wind), Ya.Kechin, K.Zhirkov, A.Kuznetsov, D.Vlasenko, P.Balanutsa, Yu.Tselik, N.Tiurina, I.Gorbunov, V.Vladimirov, D.Zimnukhov, V.Senik, A.Yudin,A.Chasovnikov, D.Cheryasov, A.Sosnovskij (Lomonosov MSU,SAI,PhysicsDepartment), O.A. Gres, N.M. Budnev (Irkutsk State University, API), C.Francile. F. Podesta, R.Podesta (Observatorio Astronomico Felix Aguilar OAFA), R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) MASTER Global robotic net (http://observ.pereplet.ru Lipunov et al.,2010,Advances in Astronomy,2010,30L) started Swift GRB 240205B/Fermi GRB 240205B observation 26 sec after notice time and 47 sec after trigger time at 2024-02-05 22:13:54 UT, with upper limit up to 15.9 mag. The observations began at zenith distance = 86 deg. (Lipunov et al. GCN 35681) MASTER auto-detection system discovered changing OT inside Swift BAT (Moss GCN 35682, Fermi GCN 25682) MASTER OT J232550.14-550704.6 R.A.,Dec(2000)=23 25 50.14 -55 07 04.6 with mOT~12.8 near maximum