GCN Circular 45456

Subject
MAXI GRB260827.40: Global MASTER-Net observations report
Event
GRB 260827.40
Date
2026-08-28T03:34:33Z (3 days ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
M. Segura,  F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA)

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 (CrAO RAS)

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)


MASTER-OAFA robotic telescope  [1]  located in Argentina (OAFA observatory of San Juan National University) started inspect of the MAXI GRB260827.40 (trigger No 279310912,17h 04m 14.40s , +24d 00m 32.4s, R=1) errorbox  219 sec after notice time and 63740 sec after trigger time at 2026-08-28 03:21:39 UT, with upper limit up to  16.9 mag. The observations began at zenith distance = 81 deg. The sun  altitude  is -61.9 deg. 

The galactic latitude b = 33 deg., longitude l = 45 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3494572

We obtain a following upper limits.  

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

   63770 | 2026-08-28 03:21:39 |         MASTER-OAFA | (17h 03m 43.44s , +24d 07m 33.8s) |   C |    60 | 16.9 |        
   63836 | 2026-08-28 03:22:44 |         MASTER-OAFA | (17h 03m 43.27s , +24d 07m 33.3s) |   C |    60 | 16.7 |        
   63901 | 2026-08-28 03:23:50 |         MASTER-OAFA | (17h 03m 43.11s , +24d 07m 32.4s) |   C |    60 | 16.5 |        
   63967 | 2026-08-28 03:24:56 |         MASTER-OAFA | (17h 03m 43.00s , +24d 07m 31.2s) |   C |    60 | 16.4 |        
   64032 | 2026-08-28 03:26:01 |         MASTER-OAFA | (17h 03m 42.85s , +24d 07m 29.7s) |   C |    60 | 16.3 |        
   64097 | 2026-08-28 03:27:06 |         MASTER-OAFA | (17h 03m 42.76s , +24d 07m 27.7s) |   C |    60 | 16.2 |        
   64163 | 2026-08-28 03:28:11 |         MASTER-OAFA | (17h 03m 42.47s , +24d 07m 27.5s) |   C |    60 | 15.8 |        
   64228 | 2026-08-28 03:29:17 |         MASTER-OAFA | (17h 03m 42.34s , +24d 07m 26.3s) |   C |    60 | 15.4 |        
   64294 | 2026-08-28 03:30:22 |         MASTER-OAFA | (17h 03m 42.31s , +24d 07m 23.8s) |   C |    60 | 15.1 |        
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