TITLE: GCN CIRCULAR NUMBER: 44625 SUBJECT: SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection DATE: 26/05/15 20:41:12 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru> A.Sosnovskij, A.Kuznetsov, V.Lipunov, I.Panchenko, P.Balanutsa, K.Zhirkov, E.Gorbovskoy, G.Antipov, N.Tiurina, Ya.Kechin, V.Senik, A.Chasovnikov, V.Topolev,D.Vlasenko, A.Sankovich, I.Gorbunov, V.Fedorova, A.Telnova (Lomonosov MSU), N.Budnev, O.Gress (ISU), F.Podesta, M.J. Segura, C.Francile, R.Podesta, E. Gonzalez (OAFA, SJNU), D.Buckley (SAAO), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich (Blagoveschensk Educational StateUniversity) R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez,J.Martinez,A.R.Corella, J.Tanori, L. Villalobos, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tavrida robotic telescope of MASTER Global Robotic Net [1-4] was pointed to the SVOM GRB260516A (Brunet et al. GCN 44622) error-box at 2026-05-15 19:19:18UT (notice time=2026-05-15 19:18:47) with upper limit up to 19.6m at single images. MASTER OT J151044.43+243321.7 / AT2026msu detection by Lomonosov MSU: MASTER-Tavrida auto-detection system discovered OT source at (RA, Dec) = 15h 10m 44.43s +24d 33m 21.7s on 2026-05-15.80648 UT. The OT magnitude (unfiltered) is 17.4m (mlim=19.1). The OT is seen in all images. There is no minor planet at this place. We have reference image on 2024-03-17.95291 UT with unfiltered mlim=19.5m. Spectral observations are required. Optical counterpart first was publishied by JinShan 100B Telescope (He et al. GCN 44623) and observed by Svom/VT (GCN 44624) Real time updated cover map and OT are available here: https://master.sai.msu.ru/site/master2/observ.php?id=3316865 [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 et al. 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/44625. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...