GCN Circular 45599

Subject
Fermi trigger No 811264269: Global MASTER-Net observations report
Date
2026-09-16T20:31:17Z (3 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 (Lomonosov MSU)

D.Buckley (SAAO),

A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)
A.Sosnovskij (Lomonosov MSU)

A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory)

L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)

R.Rebolo (The Instituto de Astrofisica de Canarias)

O.Gress, N.Budnev(ISU)

M. Segura,  F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA)


MASTER-Tavrida robotic telescope  [1]  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB260916.63 (trigger No 811264269,23h 06m 31.20s , -26d 48m 36.0s, R=8.03) errorbox  16584 sec after notice time and 16611 sec after trigger time at 2026-09-16 19:47:55 UT, with upper limit up to  18.1 mag. The observations began at zenith distance = 75 deg. The sun  altitude  is -36.8 deg. 

The galactic latitude b = -67 deg., longitude l = 29 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3505409

We obtain a following upper limits.  

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

   16701 | 2026-09-16 19:47:55 |      MASTER-Tavrida | (23h 11m 45.32s , -27d 46m 07.9s) |   C |   180 | 17.1 |        
   16689 | 2026-09-16 19:48:43 |      MASTER-Tavrida | (23h 11m 43.68s , -27d 45m 00.9s) |   C |    60 | 18.0 |        
   16793 | 2026-09-16 19:50:27 |      MASTER-Tavrida | (23h 16m 56.95s , -29d 02m 52.6s) |   C |    60 | 18.1 |        
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