GCN Circular 45415

Subject

IceCube Alert 260821A: Global MASTER-Net observations report

Event

IceCube-260821A

Date

2026-08-21T10:27:04Z (10 days ago)

Edited On

2026-08-23T21:14:24Z (8 days 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

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, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
M. Segura,  F. Podesta, R.Podesta, E. Gonzalez  (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A.Sosnovskij (CrAO),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) 

MASTER-OAFA robotic telescope  [1]  located in Argentina (OAFA observatory of San Juan National University) was pointed to the IceCube Alert 260821A (trigger No 51776820,07h 44m 40.80s , +10d 03m 00.0s, R=0.46) errorbox  22610 sec after notice time and 22930 sec after trigger time at 2026-08-21 09:56:59 UT, with upper limit up to  16.5 mag. Observations started at twilight.  The observations began at zenith distance = 76 deg. The sun  altitude  is -15.2 deg. 

The galactic latitude b = 17 deg., longitude l = 210 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3484669

We obtain a following upper limits.  

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

   22961 | 2026-08-21 09:56:59 |         MASTER-OAFA | (07h 45m 46.70s , +10d 07m 14.0s) |   C |    60 | 15.9 |        
   23036 | 2026-08-21 09:58:15 |         MASTER-OAFA | (07h 45m 48.09s , +10d 08m 19.8s) |   C |    60 | 16.0 |        
   23115 | 2026-08-21 09:59:34 |         MASTER-OAFA | (07h 45m 53.62s , +10d 07m 28.0s) |   C |    60 | 15.9 |        
   23189 | 2026-08-21 10:00:48 |         MASTER-OAFA | (07h 45m 47.68s , +10d 06m 34.3s) |   C |    60 | 16.1 |        
   23266 | 2026-08-21 10:02:05 |         MASTER-OAFA | (07h 45m 54.73s , +10d 06m 52.0s) |   C |    60 | 16.1 |        
   23419 | 2026-08-21 10:04:37 |         MASTER-OAFA | (07h 45m 51.54s , +10d 07m 21.1s) |   C |    60 | 16.3 |        
   23496 | 2026-08-21 10:05:54 |         MASTER-OAFA | (07h 45m 55.51s , +10d 08m 42.3s) |   C |    60 | 16.5 |        
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