GCN Circular 43972

Subject
Fermi GRB 260311B: Global MASTER-Net observations report
Event
GRB 260311B
Date
2026-03-12T12:32:31Z (4 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 260311B ( Fermi GBM team, GCN 43964Loading...
 
 ) errorbox  24516 sec after notice time and 24692 sec after trigger time at 2026-03-12 01:49:28 UT, with upper limit up to  15.6 mag. The observations began at zenith distance = 57 deg. The sun  altitude  is -18.9 deg. 

The galactic latitude b =  4 deg., longitude l = 32 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3181495

We obtain a following upper limits.  

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

   24723 | 2026-03-12 01:49:28 |   MASTER-Kislovodsk | (19h 10m 01.93s , +04d 53m 01.1s) |   C |    60 | 15.6 |        
   59805 | 2026-03-12 11:34:10 |             MASTER- | (18h 18m 16.48s , +06d 44m 41.9s) |   C |    60 | 17.4 |        
   59805 | 2026-03-12 11:34:10 |             MASTER- | (18h 19m 31.23s , +06d 11m 34.9s) |   C |    60 | 17.5 |        
   59876 | 2026-03-12 11:35:21 |             MASTER- | (18h 26m 26.82s , +06d 44m 33.6s) |   C |    60 | 17.2 |        
   59876 | 2026-03-12 11:35:21 |             MASTER- | (18h 27m 41.28s , +06d 11m 25.0s) |   C |    60 | 17.3 |        
   60391 | 2026-03-12 11:43:55 |             MASTER- | (18h 18m 23.46s , +06d 44m 43.7s) |   C |    60 | 17.2 |        
   60391 | 2026-03-12 11:43:55 |             MASTER- | (18h 19m 38.47s , +06d 11m 36.0s) |   C |    60 | 17.2 |        
   60478 | 2026-03-12 11:45:23 |             MASTER- | (18h 26m 21.18s , +06d 44m 18.1s) |   C |    60 | 17.3 |        
   60478 | 2026-03-12 11:45:23 |             MASTER- | (18h 27m 36.03s , +06d 11m 09.5s) |   C |    60 | 17.4 |        
   61508 | 2026-03-12 12:02:33 |             MASTER- | (18h 18m 19.70s , +06d 44m 43.2s) |   C |    60 | 17.5 |        
   61508 | 2026-03-12 12:02:33 |             MASTER- | (18h 19m 35.99s , +06d 11m 38.1s) |   C |    60 | 17.6 |        
   61579 | 2026-03-12 12:03:44 |             MASTER- | (18h 26m 26.43s , +06d 45m 59.2s) |   C |    60 | 17.5 |        
   61579 | 2026-03-12 12:03:44 |             MASTER- | (18h 27m 42.44s , +06d 12m 52.6s) |   C |    60 | 17.6 |        
   61657 | 2026-03-12 12:05:02 |             MASTER- | (18h 02m 57.54s , +06d 46m 34.6s) |   C |    60 | 17.4 |        
   61657 | 2026-03-12 12:05:02 |             MASTER- | (18h 04m 14.17s , +06d 13m 30.5s) |   C |    60 | 17.6 |        
   61729 | 2026-03-12 12:06:14 |             MASTER- | (18h 12m 23.49s , +06d 12m 17.2s) |   C |    60 | 17.5 |        
   61729 | 2026-03-12 12:06:14 |             MASTER- | (18h 11m 06.96s , +06d 45m 21.9s) |   C |    60 | 17.4 |        
   61810 | 2026-03-12 12:07:35 |             MASTER- | (18h 23m 25.76s , +08d 38m 13.5s) |   C |    60 | 17.5 |        
   61810 | 2026-03-12 12:07:35 |             MASTER- | (18h 24m 42.43s , +08d 05m 07.3s) |   C |    60 | 17.5 |        
   61890 | 2026-03-12 12:08:55 |             MASTER- | (18h 31m 28.03s , +08d 39m 36.9s) |   C |    60 | 16.7 |        
   61890 | 2026-03-12 12:08:55 |             MASTER- | (18h 32m 44.52s , +08d 06m 30.1s) |   C |    60 | 16.7 |        
   61964 | 2026-03-12 12:10:09 |             MASTER- | (18h 08m 02.64s , +08d 40m 18.8s) |   C |    60 | 17.5 |        
   61964 | 2026-03-12 12:10:09 |             MASTER- | (18h 09m 19.69s , +08d 07m 14.2s) |   C |    60 | 17.5 |        
   62053 | 2026-03-12 12:11:38 |             MASTER- | (18h 16m 02.67s , +08d 39m 09.5s) |   C |    60 | 17.8 |        
   62053 | 2026-03-12 12:11:38 |             MASTER- | (18h 17m 19.59s , +08d 06m 04.4s) |   C |    60 | 17.9 |        
   62137 | 2026-03-12 12:13:02 |             MASTER- | (18h 19m 34.48s , +06d 13m 00.2s) |   C |    60 | 17.5 |        
   62137 | 2026-03-12 12:13:02 |             MASTER- | (18h 18m 17.96s , +06d 46m 05.6s) |   C |    60 | 17.5 |        
   62213 | 2026-03-12 12:14:18 |             MASTER- | (18h 27m 43.41s , +06d 11m 45.8s) |   C |    60 | 17.6 |        
   62213 | 2026-03-12 12:14:18 |             MASTER- | (18h 26m 27.07s , +06d 44m 51.9s) |   C |    60 | 17.5 |        
   62289 | 2026-03-12 12:15:34 |             MASTER- | (18h 04m 15.28s , +06d 11m 22.4s) |   C |    60 | 17.8 |        
   62289 | 2026-03-12 12:15:34 |             MASTER- | (18h 02m 58.43s , +06d 44m 26.1s) |   C |    60 | 17.7 |        
   62361 | 2026-03-12 12:16:46 |             MASTER- | (18h 11m 08.08s , +06d 44m 34.3s) |   C |    60 | 17.5 |        
   62361 | 2026-03-12 12:16:46 |             MASTER- | (18h 12m 24.83s , +06d 11m 29.9s) |   C |    60 | 17.5 |        
   62435 | 2026-03-12 12:18:00 |             MASTER- | (18h 24m 39.81s , +08d 06m 36.2s) |   C |    60 | 17.6 |        
   62435 | 2026-03-12 12:18:00 |             MASTER- | (18h 23m 22.92s , +08d 39m 41.6s) |   C |    60 | 17.6 |        
   62534 | 2026-03-12 12:19:39 |             MASTER- | (18h 31m 28.26s , +08d 38m 04.6s) |   C |    60 | 16.7 |        
   62534 | 2026-03-12 12:19:39 |             MASTER- | (18h 32m 45.03s , +08d 04m 58.7s) |   C |    60 | 16.7 |        
   62607 | 2026-03-12 12:20:52 |             MASTER- | (18h 09m 21.12s , +08d 06m 49.7s) |   C |    60 | 17.5 |        
   62607 | 2026-03-12 12:20:52 |             MASTER- | (18h 08m 03.80s , +08d 39m 53.7s) |   C |    60 | 17.4 |        
   62679 | 2026-03-12 12:22:04 |             MASTER- | (18h 17m 19.94s , +08d 05m 57.7s) |   C |    60 | 18.0 |        
   62679 | 2026-03-12 12:22:04 |             MASTER- | (18h 16m 02.75s , +08d 39m 01.9s) |   C |    60 | 17.9 |        
   62750 | 2026-03-12 12:23:15 |             MASTER- | (18h 19m 35.12s , +06d 12m 53.1s) |   C |    60 | 17.8 |        
   62750 | 2026-03-12 12:23:15 |             MASTER- | (18h 18m 18.36s , +06d 45m 57.6s) |   C |    60 | 17.8 |        
   62825 | 2026-03-12 12:24:30 |             MASTER- | (18h 27m 42.53s , +06d 11m 38.8s) |   C |    60 | 17.7 |        
   62825 | 2026-03-12 12:24:30 |             MASTER- | (18h 26m 25.94s , +06d 44m 44.0s) |   C |    60 | 17.6 |        
   62898 | 2026-03-12 12:25:43 |             MASTER- | (18h 04m 17.41s , +06d 11m 17.9s) |   C |    60 | 17.9 |        
   62898 | 2026-03-12 12:25:43 |             MASTER- | (18h 03m 00.33s , +06d 44m 20.9s) |   C |    60 | 17.8 |        
   62970 | 2026-03-12 12:26:55 |             MASTER- | (18h 12m 26.18s , +06d 11m 27.7s) |   C |    60 | 17.6 |        
   62970 | 2026-03-12 12:26:55 |             MASTER- | (18h 11m 09.22s , +06d 44m 31.3s) |   C |    60 | 17.5 |        
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