GRB 260417B
GCN Circular 44343
Subject
Fermi GRB 260417B: Global MASTER-Net observations report
Date
2026-04-18T23:15:27Z (21 days 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, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile, 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) started inspect of the Fermi GRB 260417B ( Fermi GBM team, GCN 44331) errorbox 66043 sec after notice time and 66079 sec after trigger time at 2026-04-18 10:05:14 UT, with upper limit up to 18.4 mag. Observations started at twilight. The observations began at zenith distance = 31 deg. The sun altitude is -11.6 deg.
MASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 260417B errorbox 1 days 23747 sec after notice time and 1 days 23783 sec after trigger time at 2026-04-18 22:20:18 UT, with upper limit up to 18.7 mag. The observations began at zenith distance = 48 deg. The sun altitude is -68.6 deg.
The galactic latitude b = 1 deg., longitude l = 1 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3256668
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
23203 | 2026-04-17 22:10:08 | MASTER- | (17h 10m 25.00s , -22d 17m 31.5s) | C | 60 | 14.7 |
23280 | 2026-04-17 22:11:25 | MASTER- | (17h 25m 38.80s , -19d 39m 45.5s) | C | 60 | 13.2 |
23367 | 2026-04-17 22:12:52 | MASTER- | (17h 28m 29.57s , -18d 22m 14.8s) | C | 60 | 14.2 |
23445 | 2026-04-17 22:14:10 | MASTER- | (17h 09m 03.19s , -23d 33m 52.4s) | C | 60 | 14.9 |
24134 | 2026-04-17 22:25:39 | MASTER- | (17h 08m 12.30s , -24d 53m 35.2s) | C | 60 | 16.3 |
24217 | 2026-04-17 22:27:02 | MASTER- | (16h 56m 13.19s , -26d 09m 52.5s) | C | 60 | 15.3 |
66109 | 2026-04-18 10:05:14 | MASTER-OAFA | (17h 05m 41.45s , -21d 18m 08.8s) | C | 60 | 18.4 |
66184 | 2026-04-18 10:06:29 | MASTER-OAFA | (17h 14m 24.55s , -21d 19m 32.1s) | C | 60 | 18.0 |
66259 | 2026-04-18 10:07:44 | MASTER-OAFA | (17h 05m 42.90s , -21d 20m 07.9s) | C | 60 | 18.3 |
66335 | 2026-04-18 10:09:00 | MASTER-OAFA | (17h 14m 23.15s , -21d 20m 27.1s) | C | 60 | 18.0 |
66410 | 2026-04-18 10:10:14 | MASTER-OAFA | (17h 05m 44.83s , -21d 18m 07.3s) | C | 60 | 18.1 |
66561 | 2026-04-18 10:12:46 | MASTER-OAFA | (16h 54m 04.36s , -25d 06m 35.0s) | C | 60 | 17.9 |
110213 | 2026-04-18 22:20:18 | MASTER-SAAO | (17h 03m 25.97s , -21d 49m 48.4s) | C | 60 | 18.6 |
110399 | 2026-04-18 22:23:24 | MASTER-SAAO | (17h 17m 53.69s , -21d 35m 09.4s) | C | 60 | 18.1 |
110399 | 2026-04-18 22:23:24 | MASTER-SAAO | (17h 19m 53.70s , -21d 51m 16.9s) | C | 60 | 18.3 |
110492 | 2026-04-18 22:24:57 | MASTER-SAAO | (16h 59m 36.82s , -27d 32m 32.8s) | C | 60 | 17.5 |
110492 | 2026-04-18 22:24:57 | MASTER-SAAO | (16h 57m 30.65s , -27d 16m 26.2s) | C | 60 | 17.7 |
110586 | 2026-04-18 22:26:30 | MASTER-SAAO | (16h 59m 00.63s , -23d 27m 32.8s) | C | 60 | 18.7 |
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 44331
Subject
GRB 260417B: Fermi GBM Final Real-time Localization
Date
2026-04-17T15:54:29Z (22 days 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 LONG GRB
At 15:43:55 UT on 17 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260417B (trigger 798133440.23068 / 260417655).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 264.8, Dec = -27.4 (J2000 degrees, equivalent to J2000 17h 39m, -27d 23'), with a statistical uncertainty of 8.4 degrees.
The angle from the Fermi LAT boresight is 29.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260417655/quicklook/glg_skymap_all_bn260417655.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/bn260417655/quicklook/glg_healpix_all_bn260417655.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260417655/quicklook/glg_lc_medres34_bn260417655.gif