GCN Circular 43973

Subject
Fermi GRB 260312B: Global MASTER-Net observations report
Event
GRB 260312B
Date
2026-03-12T16:45:30Z (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 260312B ( Fermi GBM team, GCN 43969Loading...
 
 ) errorbox  24262 sec after notice time and 24340 sec after trigger time at 2026-03-12 16:32:26 UT, with upper limit up to  16.8 mag. Observations started at twilight.  The observations began at zenith distance = 80 deg. The sun  altitude  is -15.4 deg. 

The galactic latitude b = -63 deg., longitude l = 154 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3182510

We obtain a following upper limits.  

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

   24370 | 2026-03-12 16:32:26 |   MASTER-Kislovodsk | (01h 43m 41.60s , -02d 12m 39.7s) |   C |    60 | 16.1 |        
   24472 | 2026-03-12 16:34:07 |   MASTER-Kislovodsk | (01h 43m 29.55s , -00d 19m 40.6s) |   C |    60 | 16.5 |        
   24577 | 2026-03-12 16:35:53 |   MASTER-Kislovodsk | (01h 55m 57.24s , -04d 08m 01.4s) |   C |    60 | 16.8 |        
   24677 | 2026-03-12 16:37:33 |   MASTER-Kislovodsk | (01h 55m 42.13s , -02d 14m 03.2s) |   C |    60 | 16.6 |        
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