GCN Circular 45637

Subject
SVOM GRB260918.16: Global MASTER-Net observations report
Event
GRB 260918.16
Date
2026-09-18T16:56:41Z (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)

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 (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)


MASTER-OAFA robotic telescope  [1]  located in Argentina (OAFA observatory of San Juan National University) was pointed to the SVOM GRB260918.16 (trigger No 1789703236,23h 39m 12.38s , -08d 57m 15.8s, R=0.1722) errorbox  17409 sec after notice time and 18049 sec after trigger time at 2026-09-18 08:48:04 UT, with upper limit up to  20.0 mag. The observations began at zenith distance = 64 deg. The sun  altitude  is -22.6 deg. 

MASTER-Tunka robotic telescope  located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the SVOM GRB260918.16 errorbox  46199 sec after notice time and 46839 sec after trigger time at 2026-09-18 16:47:55 UT, with upper limit up to  18.3 mag. The observations began at zenith distance = 61 deg. The sun  altitude  is -36.3 deg. 

The galactic latitude b = -65 deg., longitude l = 78 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3506318

We obtain a following upper limits.  

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

   18079 | 2026-09-18 08:48:04 |         MASTER-OAFA | (23h 35m 58.37s , -10d 16m 45.6s) |   C |    60 | 19.7 |        
   18139 | 2026-09-18 08:48:04 |         MASTER-OAFA | (23h 35m 58.37s , -10d 16m 45.6s) |   C |   180 | 20.0 |  Coadd 
   18154 | 2026-09-18 08:49:19 |         MASTER-OAFA | (23h 35m 57.65s , -10d 15m 45.5s) |   C |    60 | 19.6 |        
   18232 | 2026-09-18 08:50:37 |         MASTER-OAFA | (23h 36m 03.43s , -10d 16m 46.0s) |   C |    60 | 19.6 |        
   18308 | 2026-09-18 08:51:53 |         MASTER-OAFA | (23h 35m 57.65s , -10d 17m 46.4s) |   C |    60 | 19.6 |        
   18368 | 2026-09-18 08:51:53 |         MASTER-OAFA | (23h 35m 57.65s , -10d 17m 46.5s) |   C |   180 | 20.0 |  Coadd 
   18385 | 2026-09-18 08:53:11 |         MASTER-OAFA | (23h 44m 11.71s , -10d 17m 35.0s) |   C |    60 | 19.6 |        
   18445 | 2026-09-18 08:53:11 |         MASTER-OAFA | (23h 44m 11.71s , -10d 17m 35.1s) |   C |   180 | 19.7 |  Coadd 
   18462 | 2026-09-18 08:54:27 |         MASTER-OAFA | (23h 36m 01.34s , -10d 16m 11.6s) |   C |    60 | 19.6 |        
   18539 | 2026-09-18 08:55:44 |         MASTER-OAFA | (23h 36m 01.38s , -10d 17m 43.3s) |   C |    60 | 19.6 |        
   18617 | 2026-09-18 08:57:02 |         MASTER-OAFA | (23h 44m 12.84s , -10d 16m 11.6s) |   C |    60 | 19.6 |        
   18692 | 2026-09-18 08:58:17 |         MASTER-OAFA | (23h 35m 58.15s , -10d 16m 48.8s) |   C |    60 | 19.6 |        
   18752 | 2026-09-18 08:58:17 |         MASTER-OAFA | (23h 35m 58.15s , -10d 16m 49.0s) |   C |   180 | 18.4 |  Coadd 
   21359 | 2026-09-18 09:42:44 |         MASTER-OAFA | (23h 44m 10.37s , -10d 16m 40.2s) |   C |    60 | 17.9 |        
   21434 | 2026-09-18 09:43:59 |         MASTER-OAFA | (23h 44m 10.40s , -10d 18m 11.6s) |   C |    60 | 17.7 |        
   21494 | 2026-09-18 09:43:59 |         MASTER-OAFA | (23h 44m 10.39s , -10d 18m 11.6s) |   C |   180 | 18.3 |  Coadd 
   21512 | 2026-09-18 09:45:17 |         MASTER-OAFA | (23h 44m 13.33s , -10d 16m 30.1s) |   C |    60 | 17.6 |        
   21588 | 2026-09-18 09:46:33 |         MASTER-OAFA | (23h 44m 07.61s , -10d 17m 14.1s) |   C |    60 | 17.5 |        
   21664 | 2026-09-18 09:47:49 |         MASTER-OAFA | (23h 35m 59.75s , -10d 16m 15.9s) |   C |    60 | 16.9 |        
   21741 | 2026-09-18 09:49:06 |         MASTER-OAFA | (23h 36m 05.16s , -10d 17m 16.8s) |   C |    60 | 16.6 |        
   21816 | 2026-09-18 09:50:21 |         MASTER-OAFA | (23h 35m 59.06s , -10d 18m 17.0s) |   C |    60 | 16.5 |        
   21891 | 2026-09-18 09:51:37 |         MASTER-OAFA | (23h 36m 05.58s , -10d 18m 13.3s) |   C |    60 | 16.2 |        
   46869 | 2026-09-18 16:47:55 |        MASTER-Tunka | (23h 37m 25.78s , -09d 23m 20.0s) |   C |    60 | 16.3 |        
   46870 | 2026-09-18 16:47:55 |        MASTER-Tunka | (23h 37m 12.23s , -09d 19m 16.8s) |   C |    60 | 16.4 |        
   46941 | 2026-09-18 16:49:06 |        MASTER-Tunka | (23h 37m 31.13s , -09d 23m 12.7s) |   C |    60 | 18.3 |        
   46941 | 2026-09-18 16:49:06 |        MASTER-Tunka | (23h 37m 17.57s , -09d 19m 09.4s) |   C |    60 | 18.0 |        
   47013 | 2026-09-18 16:50:18 |        MASTER-Tunka | (23h 37m 28.53s , -09d 21m 38.0s) |   C |    60 | 15.8 |        
   47013 | 2026-09-18 16:50:18 |        MASTER-Tunka | (23h 37m 14.98s , -09d 17m 34.6s) |   C |    60 | 15.2 |        
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