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Transient Alerts » in reply to GRB 261007A — GRB, X-ray Transient

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In plain words Notable

A burst of gamma rays (the most energetic form of light) was caught on 7 October 2026 by the SVOM satellite, Fermi, and several other space telescopes. It came from a patch of sky toward the constellation Cetus, and the Einstein Probe X-ray telescope also saw it. Within minutes, ground telescopes found a fading optical (visible-light) glow at the spot, and later X-ray and infrared detections confirmed it. A spectrum from the Very Large Telescope in Chile put the burst at redshift 2.101, which means the light left about 10 billion years ago. The burst lasted roughly 23 seconds, which fits the long kind of gamma-ray burst, usually produced when a massive star collapses. The glow faded from about magnitude 15 in the first minutes to about 21.6 a day later. That is a normal fading pattern for an afterglow.

How unusual is it? Most gamma-ray bursts have no measured distance, but this one has a secure spectroscopic redshift of 2.101 and a bright, well-followed afterglow seen in optical, infrared and X-ray light. That makes it notable, but it is otherwise an ordinary long burst, not one of the record-setters.

Written by an AI model (claude-sonnet-5-5) from the official reports in this thread, and rewritten as new reports arrived (version 4); last updated . It may contain mistakes: the reports themselves are the authority.

GRB 261007A: Fermi GBM observation
GCN Circulars —

GCN Circular 45830
GRB 261007A: Fermi GBM observation
From: Christian Malacaria at INAF-OAR
Issued: 2026-10-07 09:55 UTC
Type: GRB, Gamma-ray Transient

C. Malacaria (INAF-OAR) report report on behalf of the Fermi Gamma-ray Burst Monitor Team:

"At 05:39:49.71 UT on 07 October 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 261007A (trigger 813044394/261007236), which was also detected by SVOM/Eclairs (Hatsune Goto et al. 2026, GCN 45824), EP (W.F. Wen et al. 2026, GCN 45828), KAIT (W. Zheng et al. 2026, GCN 45825), and VLT (A. Saccardi et al. 2026, GCN 45829825) with a spectroscopic redshift of z = 2.101.
The Fermi GBM on-ground location is consistent with the SVOM/Eclairs position.

The angle from the Fermi LAT boresight is 92 degrees.

The GBM light curve consists of multiple bright peaks with a duration (T90) of about 22.8 s (50-300 keV).
The time-averaged spectrum from T0 to T0+36 s is best fit by a power law function with an exponential high-energy cutoff.
The power law index is -0.61 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 300 +/- 4 keV.

The event fluence (10-1000 keV) in this time interval is (9.01 +/- 0.07)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+21.7 s in the 10-1000 keV band is 43.5 +/- 0.5 ph/s/cm^2.

A Band function fits the spectrum equally well with Epeak = 293 +/- 5 keV, alpha = -0.60 +/- 0.01 and beta = -3.3 +/- 0.3.

The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: FERMIGBRST - Fermi GBM Burst Catalog (heasarc.gsfc.nasa.gov)

For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/";

Every one of the gamma-ray bursts GCN reports is posted here.
Relayed automatically from NASA's General Coordinates Network.

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