GRB 260924A: Exceptionally bright long GRB at z=3.51 with ~10^55 erg isotropic energy

AI Summary

Fermi GBM detected a long-duration gamma-ray burst (T90~338s) on 2026-09-24 at 01:13:23 UTC, also observed by Swift, Fermi-LAT, AstroSat, NuSTAR, and SVOM. The burst reached an isotropic-equivalent gamma-ray energy of ~9.74×10^54 erg at redshift z=3.51, comparable to GRB 221009A (the BOAT), making it one of the most energetic GRBs ever observed. Multi-wavelength follow-up detected bright optical/NIR afterglow, radio counterpart at 15 GHz (0.6 mJy), and confirmed the redshift via spectroscopy; IceCube found no associated neutrino events.

Measurements

Notices (1)

Fermi GBM — GRB · Thu, 24 Sep 2026 01:13:23 GMT

GCN Circulars (28)

GCN-45776 — GRB 260924A · Mon, 28 Sep 2026 17:43:09 GMT
A radio counterpart to GRB 260924A was detected at 15 GHz with a flux density of approximately 0.6 mJy using the Karl G. Jansky Very Large Array (VLA), consistent with previously reported X-ray and optical positions. This detection occurred 2.6 days after the initial burst and further observations are planned.

GCN-45775 — GRB 260924A · Mon, 28 Sep 2026 13:34:37 GMT
Swift/UVOT observed GRB 260924A with a UV grism spectrum, detecting a continuum redward of 4110 AA, consistent with a redshift of z = 3.51 due to the Lyman limit, confirming previous spectroscopic measurements.

GCN-45774 — GRB 260924A · Mon, 28 Sep 2026 08:59:15 GMT
The Abastumani Astrophysical Observatory (AbAO) detected the optical afterglow of a bright gamma-ray burst (GRB 260924A) on September 26, 2026, approximately 2 days after the initial trigger, but it was absent on the subsequent night, indicating a rapid fading of the afterglow. The observations were conducted using the AS-32 0.7m telescope in the R-band, with photometry calibrated using nearby stars from the USNO-B1.0 catalog.

GCN-45768 — GRB 260924A · Sun, 27 Sep 2026 00:54:35 GMT
The IceCube Neutrino Observatory conducted a search for muon neutrino events associated with the gamma-ray burst GRB 260924A and found no track-like events, leading to an upper limit on the muon-neutrino flux. The extended search over two days also found no significant events, confirming background expectations.

GCN-45762 — GRB 260924A · Sat, 26 Sep 2026 17:03:38 GMT
Astronomers detected the near-infrared optical counterpart of GRB 260924A in the J band with the MDM/MIRAGE instrument, approximately 2.46 days after the gamma-ray burst trigger, with an AB magnitude of 19.81 ± 0.20. The Hs band observation set an upper limit of 19.2.

GCN-45759 — GRB 260924A · Sat, 26 Sep 2026 13:04:25 GMT
The COLIBRÍ telescope detected the optical counterpart of GRB 260924A with preliminary magnitudes of r = 20.40 +/- 0.03 and z = 20.07 +/- 0.03, confirming previous observations and contributing to the study of this gamma-ray burst event.

GCN-45758 — GRB 260924A · Sat, 26 Sep 2026 10:20:10 GMT
The SYSU 80 cm infrared telescope conducted a second-epoch J-band observation of GRB 260924A approximately 44.8 hours after the initial detection, but did not detect the source down to a 5-sigma limiting magnitude of J > 18.5 mag (Vega). This non-detection provides an upper limit for the brightness of the counterpart at this time.

GCN-45751 — GRB 260924A · Fri, 25 Sep 2026 20:37:17 GMT
The Konus-Wind satellite detected a long-duration gamma-ray burst, GRB 260924A, with two distinct emission episodes and significant energy release. This burst is notable for its high isotropic energy and peak luminosity, making it one of the most energetic and luminous GRBs observed to date.

GCN-45750 — GRB 260924A · Fri, 25 Sep 2026 19:48:04 GMT
GRB 260924A, detected on September 24, 2026, is one of the most energetic gamma-ray bursts ever observed, with an isotropic-equivalent gamma-ray energy of approximately 9.74 × 10^54 erg. Its energetics are comparable to those of GRB 221009A, the Brightest Of All Time (BOAT), and continued multi-wavelength observations are encouraged.

GCN-45748 — GRB 260924A · Fri, 25 Sep 2026 17:19:12 GMT
The GRB 260924A was observed using the 40cm SLT and 1m LOT telescopes at the Lulin Observatory, detecting an optical counterpart with magnitudes of 19.2 ± 0.1 in the g-band and 18.38 ± 0.04 in the r-band. These observations confirm the presence of the GRB and its optical transient, aligning with previous detections by other observatories.

GCN-45743 — GRB 260924A · Fri, 25 Sep 2026 12:06:46 GMT
The optical afterglow of GRB 260924A was detected by the D50 telescope at the Astronomical Institute Ondrejov, with a magnitude of r' = 19.12 +/- 0.08 (AB) at a mean epoch of T0+26.4 hours. This detection is consistent with previous UVOT position measurements and provides additional data for studying the gamma-ray burst event.

GCN-45741 — GRB 260924A · Fri, 25 Sep 2026 09:22:35 GMT
The SVOM/GRM instrument detected GRB 260924A, a gamma-ray burst with a duration of 338 seconds, which was also observed by Fermi, Swift, and AstroSat. The burst's spectrum and localization were analyzed, revealing significant energy release and positioning it in key astrophysical relation diagrams.

GCN-45740 — GRB 260924A · Fri, 25 Sep 2026 08:46:21 GMT
The gamma-ray burst GRB 260924A, detected by multiple observatories, has been spectroscopically confirmed to have a redshift of z = 3.51, placing it among the most distant and luminous optical afterglows observed. This redshift was determined using the 2.2m telescope at the Calar Alto Observatory, which identified the Lyman-alpha break and Lyman limit in the afterglow spectrum.

GCN-45736 — GRB 260924A · Fri, 25 Sep 2026 02:41:33 GMT
The SYSU 80 cm infrared telescope detected the optical counterpart of GRB 260924A in the J-band, measuring a magnitude of 17.13 Vega mag. This observation was conducted approximately 20.6 hours after the initial detection by Fermi/GBM and Swift/BAT.

GCN-45735 — GRB 260924A · Fri, 25 Sep 2026 01:37:57 GMT
The Swift/UVOT telescope detected a source consistent with the XRT position of GRB 260924A, providing preliminary UVOT positions and magnitudes in various filters. The detection occurred 158 seconds after the BAT trigger, with an estimated uncertainty of 0.50 arc seconds.

GCN-45734 — GRB 260924A · Fri, 25 Sep 2026 00:00:05 GMT
The GROWTH-India Telescope detected the optical counterpart of GRB 260924A, a gamma-ray burst initially detected by the Fermi satellite, approximately 21.4 hours after the event. The observations, conducted in the SDSS r' and g' filters, measured magnitudes of 18.68 +/- 0.03 and 19.63 +/- 0.04, respectively, consistent with other reported observations.

GCN-45733 — GRB 260924A · Thu, 24 Sep 2026 21:08:37 GMT
The Swift-BAT team has refined the analysis of GRB 260924A, determining a precise position and multi-peaked light curve structure. The event, detected on September 24, 2024, exhibited a complex temporal profile with a significant fluence and peak photon flux.

GCN-45732 — GRB 260924A · Thu, 24 Sep 2026 19:26:01 GMT
NuSTAR detected prompt emission from the long-duration GRB 260924A, also observed by Fermi-GBM, Swift-BAT, and AstroSat-CZTI, with a multi-peaked burst lasting about 150 seconds and a peak count rate of approximately 1500 cps. The Swift-XRT localization implies significant offsets from the NuSTAR boresight and geocenter.

GCN-45731 — GRB 260924A · Thu, 24 Sep 2026 19:14:45 GMT
Swift/UVOT began observing the field of GRB 260924A 158 seconds after the BAT trigger but detected no optical afterglow consistent with the XRT position. Preliminary 3-sigma upper limits for various filters were provided, with magnitudes not corrected for Galactic extinction.

GCN-45730 — GRB 260924A · Thu, 24 Sep 2026 18:40:46 GMT
The Swift-XRT team has analyzed data from GRB 260924A, finding a late-time light curve with an initial power-law decay followed by a break, and a spectrum consistent with an absorbed power-law. The photon index and absorption column density have been determined, with the count rate and flux expected to decay further over the next 24 hours.

GCN-45723 — GRB 260924A · Thu, 24 Sep 2026 13:56:57 GMT
On 24 September 2026, the Fermi Gamma-ray Burst Monitor (GBM) detected a gamma-ray burst (GRB 260924A) which was also observed by multiple other telescopes including Swift-BAT, Swift-XRT, AstroSat CZTI, and Fermi-LAT. The event had a duration of approximately 337.9 seconds and was characterized by three distinct emission episodes, with significant spectral and temporal analysis provided.

GCN-45721 — GRB 260924A · Thu, 24 Sep 2026 12:00:30 GMT
On September 24th, 2026, the Fermi-LAT detected a bright gamma-ray burst (GRB 260924A) with high-energy emission, also observed by multiple other telescopes. The burst had a significant photon flux above 100 MeV and the highest-energy photon detected was 43.3 GeV.

GCN-45720 — GRB 260924A · Thu, 24 Sep 2026 11:11:28 GMT
The AstroSat CZTI collaboration detected a gamma-ray burst, GRB 260924A, on September 24, 2026. The burst was also detected by Fermi and Swift BAT, showing two distinct emission peaks and a T90 duration of 336 seconds.

GCN-45718 — GRB 260924A · Thu, 24 Sep 2026 07:35:16 GMT
The Nordic Optical Telescope (NOT) observed the field of GRB 260924A and detected a source with coordinates RA (J2000) = 08:55:03.10, Dec (J2000) = +12:02:35.42, confirming the presence of an optical counterpart. The source was measured to have AB magnitudes of r = 16.28 and z = 16.00, calibrated using nearby objects from the Pan-STARRS catalog.

GCN-45717 — GRB 260924A · Thu, 24 Sep 2026 07:10:50 GMT
The 1.5m OSN telescope detected a bright optical afterglow from GRB 260924A, with a magnitude of R=15.5, approximately 3.18 hours post-trigger. This detection was made following initial observations by the Fermi and Swift satellites, and spectroscopic observations are encouraged to further study the event.

GCN-45715 — GRB 260924A · Thu, 24 Sep 2026 05:11:47 GMT
The Swift-XRT team has reported an enhanced position for the gamma-ray burst GRB 260924A, with coordinates RA (J2000): 08h 55m 03.07s and Dec (J2000): +12d 02' 35.7" and an uncertainty of 2.1 arcsec. This position is based on XRT Photon Counting mode data and UVOT images, and may be further refined as more data is received.

GCN-45713 — GRB 260924A · Thu, 24 Sep 2026 01:41:46 GMT
The Swift Burst Alert Telescope (BAT) detected a gamma-ray burst, GRB 260924A, at 01:13:28 UT on 26/09/24. The burst had a complex structure with a duration of at least 20 seconds and a peak count rate of ~3700 counts/sec. The XRT instrument on Swift located a bright, uncatalogued X-ray source within the BAT error circle, but no optical afterglow was detected by the UVOT.

GCN-45712 — GRB 260924A · Thu, 24 Sep 2026 01:23:59 GMT
The Fermi Gamma-ray Burst Monitor (GBM) detected a likely long gamma-ray burst (GRB 260924A) on September 24, 2026, at 01:13:23 UT. The event was located at RA = 139.9, Dec = 9.7 (J2000) with a statistical uncertainty of 1.6 degrees.