GRB 261003A
GCN Circular 45799
Subject
Fermi GRB 261003A: Global MASTER-Net observations report
Date
2026-10-03T02:45:49Z (7 hours ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
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)
O.Gress, N.Budnev(ISU)
M. Segura, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA)
MASTER-Tavrida robotic telescope [1] located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 261003A ( Fermi GBM team, GCN 45797) errorbox 4620 sec after notice time and 4654 sec after trigger time at 2026-10-03 02:36:10 UT, with upper limit up to 16.5 mag. Observations started at twilight. The observations began at zenith distance = 80 deg. The sun altitude is -12.5 deg.
The galactic latitude b = 4 deg., longitude l = 83 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3517714
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
4660 | 2026-10-03 02:36:10 | MASTER-Tavrida | (19h 21m 38.90s , +53d 18m 43.8s) | C | 10 | 15.7 |
4673 | 2026-10-03 02:36:22 | MASTER-Tavrida | (19h 21m 38.98s , +53d 18m 43.0s) | C | 10 | 15.7 |
4673 | 2026-10-03 02:36:23 | MASTER-Tavrida | (19h 21m 33.52s , +53d 20m 03.7s) | C | 10 | 14.2 |
4687 | 2026-10-03 02:36:36 | MASTER-Tavrida | (19h 21m 39.10s , +53d 18m 43.1s) | C | 10 | 15.8 |
4687 | 2026-10-03 02:36:36 | MASTER-Tavrida | (19h 21m 33.60s , +53d 20m 04.4s) | C | 10 | 14.1 |
4705 | 2026-10-03 02:36:50 | MASTER-Tavrida | (19h 21m 39.22s , +53d 18m 43.0s) | C | 20 | 16.2 |
4706 | 2026-10-03 02:36:50 | MASTER-Tavrida | (19h 21m 33.74s , +53d 20m 04.6s) | C | 20 | 14.6 |
4729 | 2026-10-03 02:37:13 | MASTER-Tavrida | (19h 21m 39.35s , +53d 18m 43.2s) | C | 20 | 16.0 |
4756 | 2026-10-03 02:37:36 | MASTER-Tavrida | (19h 21m 39.48s , +53d 18m 43.1s) | C | 30 | 16.2 |
4756 | 2026-10-03 02:37:36 | MASTER-Tavrida | (19h 21m 33.97s , +53d 20m 05.5s) | C | 30 | 14.6 |
4790 | 2026-10-03 02:38:10 | MASTER-Tavrida | (19h 21m 39.60s , +53d 18m 43.8s) | C | 30 | 16.3 |
4790 | 2026-10-03 02:38:10 | MASTER-Tavrida | (19h 21m 34.10s , +53d 20m 06.4s) | C | 30 | 14.6 |
4829 | 2026-10-03 02:38:43 | MASTER-Tavrida | (19h 21m 39.63s , +53d 18m 44.3s) | C | 40 | 16.4 |
4829 | 2026-10-03 02:38:44 | MASTER-Tavrida | (19h 21m 34.15s , +53d 20m 07.0s) | C | 40 | 14.9 |
4878 | 2026-10-03 02:39:27 | MASTER-Tavrida | (19h 21m 39.67s , +53d 18m 45.2s) | C | 50 | 16.5 |
4878 | 2026-10-03 02:39:27 | MASTER-Tavrida | (19h 21m 34.17s , +53d 20m 08.5s) | C | 50 | 14.9 |
4937 | 2026-10-03 02:40:21 | MASTER-Tavrida | (19h 21m 39.72s , +53d 18m 46.8s) | C | 60 | 16.5 |
4937 | 2026-10-03 02:40:21 | MASTER-Tavrida | (19h 21m 34.22s , +53d 20m 10.4s) | C | 60 | 14.9 |
5007 | 2026-10-03 02:41:27 | MASTER-Tavrida | (19h 21m 39.75s , +53d 18m 48.6s) | C | 70 | 16.5 |
5007 | 2026-10-03 02:41:27 | MASTER-Tavrida | (19h 21m 34.25s , +53d 20m 12.4s) | C | 70 | 14.9 |
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
GCN Circular 45797
Subject
GRB 261003A: Fermi GBM Final Real-time Localization
Date
2026-10-03T01:29:04Z (8 hours ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
The Fermi GBM team reports the detection of a likely SHORT GRB
At 01:18:35 UT on 3 Oct 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 261003A (trigger 812683120.140818 / 261003055).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 306.5, Dec = 45.7 (J2000 degrees, equivalent to J2000 20h 26m, 45d 42'), with a statistical uncertainty of 20.7 degrees.
The angle from the Fermi LAT boresight is 87.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn261003055/quicklook/glg_skymap_all_bn261003055.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn261003055/quicklook/glg_healpix_all_bn261003055.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn261003055/quicklook/glg_lc_medres34_bn261003055.gif