GCN Circular 43801

Subject
Fermi GRB 260221B: Global MASTER-Net observations report
Event
GRB 260221B
Date
2026-02-22T02:30:42Z (a day ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
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 260221B ( Fermi GBM team, GCN 43800Loading...
 
 ) errorbox  9789 sec after notice time and 9824 sec after trigger time at 2026-02-22 02:02:07 UT, with upper limit up to  15.3 mag. The observations began at zenith distance = 52 deg. The sun  altitude  is -22.0 deg. 

The galactic latitude b = 16 deg., longitude l = 112 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3150150

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

    9855 | 2026-02-22 02:02:07 |   MASTER-Kislovodsk | (21h 49m 42.78s , +74d 56m 55.5s) |   C |    60 | 12.5 |        
    9970 | 2026-02-22 02:04:03 |   MASTER-Kislovodsk | (21h 29m 11.14s , +73d 03m 13.8s) |   C |    60 | 15.3 |        
   10074 | 2026-02-22 02:05:47 |   MASTER-Kislovodsk | (21h 30m 08.15s , +73d 03m 12.4s) |   C |    60 | 12.1 |        
   10227 | 2026-02-22 02:08:19 |   MASTER-Kislovodsk | (21h 23m 43.72s , +76d 53m 40.4s) |   C |    60 | 14.2 |        
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