GCN Circular 45506

Subject
SVOM GRB260903A: Global MASTER-Net observations report
Event
GRB 260903A
Date
2026-09-03T21:45:45Z (a day ago)
Edited On
2026-09-04T19:32:33Z (8 hours ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Vladimir Lipunov at Lomonosov Moscow State University, MASTER Global Robotic NET PI <lipunov2007@gmail.com>
Via
O.Gress, N.Budnev(ISU)

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)

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


MASTER-Tunka robotic telescope  [1]  located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the SVOM GRB260903.53 (trigger No 1788439007,01h 42m 14.86s , +11d 13m 58.1s, R=0.198) errorbox  7913 sec after notice time and 9200 sec after trigger time at 2026-09-03 15:10:07 UT, with upper limit up to  18.8 mag. The observations began at zenith distance = 70 deg. The sun  altitude  is -25.7 deg. 

The galactic latitude b = -49 deg., longitude l = 143 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3498603

We obtain a following upper limits.  

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

    9230 | 2026-09-03 15:10:07 |        MASTER-Tunka | (01h 39m 56.83s , +10d 45m 37.2s) |   C |    60 | 13.9 |        
    9303 | 2026-09-03 15:11:19 |        MASTER-Tunka | (01h 40m 02.09s , +10d 45m 48.3s) |   C |    60 | 16.4 |        
    9379 | 2026-09-03 15:12:35 |        MASTER-Tunka | (01h 39m 58.94s , +10d 47m 16.3s) |   C |    60 | 16.9 |        
    9454 | 2026-09-03 15:13:51 |        MASTER-Tunka | (01h 39m 59.00s , +10d 45m 42.4s) |   C |    60 | 16.0 |        
    9528 | 2026-09-03 15:15:04 |        MASTER-Tunka | (01h 40m 01.06s , +10d 47m 25.9s) |   C |    60 | 16.3 |        
    9603 | 2026-09-03 15:16:19 |        MASTER-Tunka | (01h 39m 55.32s , +10d 46m 25.1s) |   C |    60 | 16.9 |        
    9709 | 2026-09-03 15:18:05 |        MASTER-Tunka | (01h 39m 55.09s , +10d 47m 22.5s) |   C |    60 | 16.9 |        
    9789 | 2026-09-03 15:19:25 |        MASTER-Tunka | (01h 40m 02.37s , +10d 46m 21.1s) |   C |    60 | 17.3 |        
    9867 | 2026-09-03 15:20:43 |        MASTER-Tunka | (01h 39m 56.82s , +10d 45m 15.9s) |   C |    60 | 16.5 |        
    9945 | 2026-09-03 15:22:01 |        MASTER-Tunka | (01h 40m 01.29s , +10d 45m 27.8s) |   C |    60 | 17.6 |        
    9991 | 2026-09-03 15:22:48 |        MASTER-Tunka | (01h 39m 59.00s , +10d 46m 53.3s) |   C |    60 | 18.0 |        
   10064 | 2026-09-03 15:24:01 |        MASTER-Tunka | (01h 39m 58.96s , +10d 45m 21.6s) |   C |    60 | 17.4 |        
   10140 | 2026-09-03 15:25:16 |        MASTER-Tunka | (01h 40m 02.07s , +10d 47m 05.4s) |   C |    60 | 17.2 |        
   10212 | 2026-09-03 15:26:28 |        MASTER-Tunka | (01h 39m 55.16s , +10d 46m 05.9s) |   C |    60 | 17.8 |        
   10285 | 2026-09-03 15:27:41 |        MASTER-Tunka | (01h 39m 56.15s , +10d 47m 03.1s) |   C |    60 | 17.1 |        
   10360 | 2026-09-03 15:28:56 |        MASTER-Tunka | (01h 40m 02.39s , +10d 46m 01.4s) |   C |    60 | 17.6 |        
   10432 | 2026-09-03 15:30:08 |        MASTER-Tunka | (01h 39m 55.93s , +10d 44m 58.5s) |   C |    60 | 17.2 |        
   10504 | 2026-09-03 15:31:21 |        MASTER-Tunka | (01h 40m 00.97s , +10d 45m 24.5s) |   C |    60 | 17.5 |        
   10580 | 2026-09-03 15:32:36 |        MASTER-Tunka | (01h 39m 58.90s , +10d 46m 27.8s) |   C |    60 | 18.3 |        
   10653 | 2026-09-03 15:33:49 |        MASTER-Tunka | (01h 39m 58.86s , +10d 44m 58.2s) |   C |    60 | 18.1 |        
   10725 | 2026-09-03 15:35:01 |        MASTER-Tunka | (01h 40m 02.87s , +10d 46m 32.3s) |   C |    60 | 17.0 |        
   10832 | 2026-09-03 15:36:48 |        MASTER-Tunka | (01h 39m 55.80s , +10d 45m 47.7s) |   C |    60 | 17.4 |        
   10911 | 2026-09-03 15:38:07 |        MASTER-Tunka | (01h 39m 56.49s , +10d 46m 44.1s) |   C |    60 | 18.1 |        
   10956 | 2026-09-03 15:38:53 |        MASTER-Tunka | (01h 40m 01.47s , +10d 45m 43.1s) |   C |    60 | 18.1 |        
   11065 | 2026-09-03 15:40:41 |        MASTER-Tunka | (01h 39m 55.52s , +10d 44m 39.4s) |   C |    60 | 18.2 |        
   11143 | 2026-09-03 15:41:59 |        MASTER-Tunka | (01h 40m 02.63s , +10d 44m 49.8s) |   C |    60 | 18.8 |        
   11221 | 2026-09-03 15:43:17 |        MASTER-Tunka | (01h 39m 58.80s , +10d 46m 16.3s) |   C |    60 | 18.3 |        
   11266 | 2026-09-03 15:44:03 |        MASTER-Tunka | (01h 39m 58.83s , +10d 44m 53.9s) |   C |    60 | 18.1 |        
   11337 | 2026-09-03 15:45:14 |        MASTER-Tunka | (01h 40m 01.35s , +10d 46m 05.4s) |   C |    60 | 18.3 |        
   11412 | 2026-09-03 15:46:28 |        MASTER-Tunka | (01h 39m 55.82s , +10d 45m 27.4s) |   C |    60 | 18.2 |        
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