TITLE: GCN CIRCULAR NUMBER: 43797 SUBJECT: Fermi GRB 260221A: Global MASTER-Net observations report DATE: 26/02/21 19:00:32 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), 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, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 260221A ( Fermi GBM team, GCN 43795) errorbox 1055 sec after notice time and 1088 sec after trigger time at 2026-02-21 16:41:00 UT, with upper limit up to 12.4 mag. The observations began at zenith distance = 74 deg. The sun altitude is -21.2 deg. MASTER-Tunka robotic telescope located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 260221A errorbox 5336 sec after notice time and 5369 sec after trigger time at 2026-02-21 17:52:21 UT, with upper limit up to 16.0 mag. The observations began at zenith distance = 30 deg. The sun altitude is -49.0 deg. The galactic latitude b = 61 deg., longitude l = 96 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3149550 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 1118 | 2026-02-21 16:41:00 | MASTER-Kislovodsk | (13h 44m 40.23s , +50d 10m 34.6s) | C | 60 | 12.4 | 1657 | 2026-02-21 16:49:59 | MASTER-Kislovodsk | (13h 49m 30.45s , +48d 15m 50.3s) | C | 60 | 12.0 | 5399 | 2026-02-21 17:52:21 | MASTER-Tunka | (14h 07m 03.52s , +53d 13m 43.3s) | C | 60 | 15.9 | 5399 | 2026-02-21 17:52:21 | MASTER-Tunka | (14h 07m 59.88s , +53d 08m 17.6s) | C | 60 | 16.0 | 5473 | 2026-02-21 17:53:35 | MASTER-Tunka | (14h 20m 10.09s , +51d 18m 47.8s) | C | 60 | 15.9 | 5473 | 2026-02-21 17:53:35 | MASTER-Tunka | (14h 21m 02.69s , +51d 13m 17.9s) | C | 60 | 15.9 | 5547 | 2026-02-21 17:54:48 | MASTER-Tunka | (14h 19m 45.21s , +55d 07m 57.6s) | C | 60 | 15.6 | 5547 | 2026-02-21 17:54:48 | MASTER-Tunka | (14h 20m 44.18s , +55d 02m 30.8s) | C | 60 | 15.5 | 5621 | 2026-02-21 17:56:03 | MASTER-Tunka | (14h 10m 13.14s , +49d 24m 43.5s) | C | 60 | 15.2 | 5621 | 2026-02-21 17:56:03 | MASTER-Tunka | (14h 11m 03.71s , +49d 19m 11.0s) | C | 60 | 15.1 | 5695 | 2026-02-21 17:57:17 | MASTER-Tunka | (14h 32m 57.97s , +53d 06m 17.2s) | C | 60 | 14.4 | 5696 | 2026-02-21 17:57:17 | MASTER-Tunka | (14h 32m 03.19s , +53d 11m 49.2s) | C | 60 | 14.5 | 5770 | 2026-02-21 17:58:31 | MASTER-Tunka | (13h 56m 11.18s , +51d 17m 55.4s) | C | 60 | 15.6 | 5770 | 2026-02-21 17:58:31 | MASTER-Tunka | (13h 57m 05.52s , +51d 12m 26.1s) | C | 60 | 15.5 | 5844 | 2026-02-21 17:59:46 | MASTER-Tunka | (13h 53m 32.03s , +55d 08m 06.5s) | C | 60 | 15.3 | 5844 | 2026-02-21 17:59:46 | MASTER-Tunka | (13h 54m 33.24s , +55d 02m 18.8s) | C | 60 | 15.2 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43797. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...