GCN Circular 43944

Subject
Fermi GRB 260307A: Global MASTER-Net observations report
Event
GRB 260307A
Date
2026-03-08T03:00:45Z (2 days 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 260307A ( Fermi GBM team, GCN 43939Loading...
 
 ) errorbox  52522 sec after notice time and 52542 sec after trigger time at 2026-03-08 02:03:41 UT, with upper limit up to  17.6 mag. The observations began at zenith distance = 27 deg. The sun  altitude  is -17.6 deg. 

The galactic latitude b = 75 deg., longitude l = 43 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3173784

We obtain a following upper limits.  

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

   52573 | 2026-03-08 02:03:41 |   MASTER-Kislovodsk | (13h 56m 48.56s , +30d 11m 50.0s) |   C |    60 | 17.5 |        
   52671 | 2026-03-08 02:05:19 |   MASTER-Kislovodsk | (13h 55m 18.49s , +28d 17m 01.2s) |   C |    60 | 17.3 |        
   52762 | 2026-03-08 02:06:51 |   MASTER-Kislovodsk | (13h 41m 41.44s , +28d 16m 16.9s) |   C |    60 | 17.1 |        
   52862 | 2026-03-08 02:08:30 |   MASTER-Kislovodsk | (13h 42m 54.18s , +30d 11m 08.6s) |   C |    60 | 17.4 |        
   53171 | 2026-03-08 02:13:40 |   MASTER-Kislovodsk | (13h 54m 42.32s , +26d 22m 26.2s) |   C |    60 | 17.4 |        
   53271 | 2026-03-08 02:15:20 |   MASTER-Kislovodsk | (13h 41m 19.11s , +26d 22m 57.5s) |   C |    60 | 17.6 |        
   53368 | 2026-03-08 02:16:57 |   MASTER-Kislovodsk | (14h 08m 52.75s , +28d 17m 54.2s) |   C |    60 | 17.2 |        
   53469 | 2026-03-08 02:18:38 |   MASTER-Kislovodsk | (14h 09m 29.84s , +28d 17m 50.9s) |   C |    60 | 12.1 |        
   53580 | 2026-03-08 02:20:28 |   MASTER-Kislovodsk | (13h 48m 25.23s , +33d 57m 51.7s) |   C |    60 | 17.3 |        
   54177 | 2026-03-08 02:30:26 |   MASTER-Kislovodsk | (14h 08m 06.54s , +26d 23m 27.0s) |   C |    60 | 17.3 |        
   54278 | 2026-03-08 02:32:07 |   MASTER-Kislovodsk | (14h 13m 24.07s , +32d 04m 29.5s) |   C |    60 | 17.4 |        
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