GCN Circular 45682

Subject
EP Alert 260921.58: Global MASTER-Net observations report
Date
2026-09-21T17:27:39Z (3 days ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
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 (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)

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 EP Alert 260921.58 (trigger No 1709319528,23h 55m 27.60s , +22d 11m 56.4s, R=0.0516178) errorbox  11189 sec after notice time and 11607 sec after trigger time at 2026-09-21 17:14:43 UT, with upper limit up to  20.1 mag. The observations began at zenith distance = 30 deg. The sun  altitude  is -37.4 deg. 

The galactic latitude b = -39 deg., longitude l = 107 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3508589

We obtain a following upper limits.  

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

   11637 | 2026-09-21 17:14:43 |        MASTER-Tunka | (23h 53m 17.41s , +21d 51m 04.5s) |   C |    60 | 19.9 |        
   11637 | 2026-09-21 17:14:43 |        MASTER-Tunka | (23h 53m 42.91s , +21d 45m 41.1s) |   C |    60 | 19.7 |        
   11713 | 2026-09-21 17:15:59 |        MASTER-Tunka | (23h 53m 23.85s , +21d 50m 00.9s) |   C |    60 | 19.8 |        
   11713 | 2026-09-21 17:15:59 |        MASTER-Tunka | (23h 53m 49.32s , +21d 44m 37.0s) |   C |    60 | 19.6 |        
   11787 | 2026-09-21 17:17:13 |        MASTER-Tunka | (23h 53m 43.46s , +21d 43m 34.1s) |   C |    60 | 19.2 |        
   11787 | 2026-09-21 17:17:13 |        MASTER-Tunka | (23h 53m 18.00s , +21d 48m 58.2s) |   C |    60 | 19.5 |        
   11861 | 2026-09-21 17:18:27 |        MASTER-Tunka | (23h 53m 23.29s , +21d 49m 21.8s) |   C |    60 | 19.8 |        
   11861 | 2026-09-21 17:18:27 |        MASTER-Tunka | (23h 53m 48.75s , +21d 43m 57.7s) |   C |    60 | 19.6 |        
   11934 | 2026-09-21 17:19:40 |        MASTER-Tunka | (23h 53m 45.40s , +21d 45m 01.4s) |   C |    60 | 19.7 |        
   11934 | 2026-09-21 17:19:40 |        MASTER-Tunka | (23h 53m 19.94s , +21d 50m 25.6s) |   C |    60 | 19.9 |        
   12008 | 2026-09-21 17:20:54 |        MASTER-Tunka | (23h 53m 19.88s , +21d 49m 10.4s) |   C |    60 | 20.1 |        
   12008 | 2026-09-21 17:20:54 |        MASTER-Tunka | (23h 53m 45.31s , +21d 43m 46.3s) |   C |    60 | 19.9 |        
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