TITLE: GCN CIRCULAR NUMBER: 43006 SUBJECT: Swift GRB 251205A : MASTER OT detection with host galaxy DATE: 25/12/06 01:42:41 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru> V.M. Lipunov (Lomonosov MSU), V.Senik, E.Gorbovskoy, A.Kuznetsov, I.Panchenko, G.Antipov, P.Balanutsa, K.Zhirkov, N. Tiurina, Ya.Kechin,A.Chasovnikov, D.Vlasenko, Yu.Tselik(Lomonosov MSU, SAI, Moscow), O.A.Gress, N.M.Budnev, O.Ershova (Irkutsk State University), R. Podesta, C.Francile, F. Podesta, E. Gonzalez (OAFA, San JuanUni.,Argentina); D.Buckley (SAAO), A. Sosnovskij (CrAO RAS), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysic Observatory, Mexico) V.M.Pillet, R.Rebolo Lopez (The Instituto de Astrofisica de Canarias,Spain) MASTER-Kislovodsk robotic telescope of MASTER Global Robotic Net (Lipunov et al. [1-4], http://observ.pereplet.ru ), started Swift GRB 251205A (Lanava et al GCN 43005) error-box observations in alert mode (PP filters) 19s after notice time at at 2025-12-05 23:41:19 UT, Lipunov et al. GCN 43004 MASTER auto-detection system found optical counterpart MASTER OT J132105.37+295545.8 , first publishied by Swift (GCN 43005) with unfiltered m_OT~18.1m We have also prompt wide-field cameras images, the reduction will be later. There is host(possible) galaxy in 4.36" from GRB counterpart with z_phot=0.25470(Cavuoti et al. 2014) Real time updated cover map and OT position are available here: https://master.sai.msu.ru/site/master2/observ.php?id=3062088 Observation and reduction will continue. [1] Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L [2] Lipunov et al. 2022, Universe, Vol. 8(5), id.271 [3] Lipunov et a. 2019, ARep, vol.63, 293 [4] Lipunov V., Kornilov V., Gorbovskoy E., Tiurina N., Kuznetsov A. 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics,Lomonosov MSU PRESS, 591pp. http://www.pereplet.ru/lipunov/625.html#625 View this GCN Circular online at https://gcn.nasa.gov/circulars/43006. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...