TITLE: GCN CIRCULAR NUMBER: 44023 SUBJECT: IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate DATE: 26/03/15 18:39:46 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru> M.J. Segura, C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), Ya.Kechin, V.Lipunov (Lomonosov MSU), N.Budnev, O.Gress (ISU), A.Kuznetsov, I.Panchenko, P.Balanutsa, G.Antipov, E.Gorbovskoy, N.Tiurina, V.Senik, A.Chasovnikov, M.Shilova,V.Topolev, D.Vlasenko, A.Sankovich, Yu.Tselik (Lomonosov MSU), D.Svinkin (Ioffe Institute), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), D.Buckley (SAAO), 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) A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) MASTER OT J114437.99-023613.5/AT 2026fpm discovery MASTER-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) was pointed to the IceCube Alert 260315A (trigger No 46886533,11h 42m 40.32s , -01d 53m 06.0s, R=0.71) errorbox 105 sec after notice time and 224 sec after trigger time at 2026-03-15 02:22:50 UT, with upper limit up to 20.4 mag. The observations began at zenith distance = 45 deg. The sun altitude is -42.8 deg. The galactic latitude b = 57 deg., longitude l = 272 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3187113 MASTER-OAFA auto-detection system [4] discovered OT source at (RA, Dec) = 11h 44m 37.99s -02d 36m 13.5s on 2026-03-15.10943 UT very close to center of neutrino errorbox (GCN Circular #44017). The OT magnitude in 'CLEAR' filter is 19.2m (mlim = 20.0). The OT is seen in 44 images. There is no minor planet at this place. We have reference image on 2026-02-12.28608 UT with 'FAULT' filter 19.9m. Spectral observations are required. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/114437.99-023613.5.png [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/44023. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...