GCN Circular 45908
EP261007b: Global MASTER-Net observations report
From: Vladimir Lipunov at Moscow State U/Krylov Obs
Issued: 2026-10-11 19:45 UTC

D.Buckley (SAAO),

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)

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)

O.Gress, N.Budnev(ISU)

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


MASTER-SAAO robotic telescope [1] located in South Africa (South African Astronomical Observatory) was pointed to the EP261007b ( EP Team at NAOC/CAS <ep_ta@bao.ac.cn> et al., GCN 45847) errorbox 13291 sec after notice time and 1 days 53720 sec after trigger time at 2026-10-11 19:38:56 UT, with upper limit up to 19.4 mag. The observations began at zenith distance = 47 deg. The sun altitude is -34.6 deg.

The galactic latitude b = -48 deg., longitude l = 99 deg.


Real time updated cover map and OT discovered available here:
GRB261010.20 page :: MASTER Database :: MASTER Net (master.sai.msu.ru)

We obtain a following upper limits.

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

140150 | 2026-10-11 19:38:56 | MASTER-SAAO | (23h 41m 29.50s , +11d 13m 26.5s) | C | 60 | 19.3 |
140150 | 2026-10-11 19:38:56 | MASTER-SAAO | (23h 43m 18.80s , +10d 57m 54.6s) | C | 60 | 19.0 |
140244 | 2026-10-11 19:40:30 | MASTER-SAAO | (23h 41m 35.25s , +11d 12m 30.9s) | C | 60 | 19.4 |
140244 | 2026-10-11 19:40:30 | MASTER-SAAO | (23h 43m 24.47s , +10d 56m 58.3s) | C | 60 | 19.1 |
140337 | 2026-10-11 19:42:02 | MASTER-SAAO | (23h 43m 19.19s , +10d 56m 01.2s) | C | 60 | 19.1 |
140337 | 2026-10-11 19:42:02 | MASTER-SAAO | (23h 41m 29.91s , +11d 11m 33.9s) | C | 60 | 19.3 |
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

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