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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 / EP261007a: NuSTAR detection of prompt emission
GCN Circulars —

GCN Circular 45846
GRB 261007A / EP261007a: NuSTAR detection of prompt emission
From: Gaurav Waratkar at Caltech
Issued: 2026-10-08 02:06 UTC
Type: GRB, X-ray Transient

G. Waratkar (Caltech) and B. Grefenstette (Caltech) report on behalf of the NuSTAR Search for INteresting Gamma-ray Signals (SINGS) working group:

The NuSTAR SINGS working group reports the detection of prompt emission from the long-duration GRB 261007A, associated with EP261007a, in both the NuSTAR CsI anti-coincidence shields. This GRB was identified through a blind search using the CsI shield rates. Details of the search algorithm will be described in a future paper.

The NuSTAR SINGS algorithm triggered at 2026-10-07T05:39:49.7 UTC shows a detection of GRB 261007A, detected by SVOM (GCN 45824), Fermi-GBM (GCN 45830), and associated with EP261007a detected by Einstein Probe (GCN 45828).

The NuSTAR CsI shield data are recorded at 1 Hz. We detect a two-peak burst lasting for about 30-s, consistent with the GBM lightcurve. The peak count rate is ~4000-cps with a baseline rate of ~1000-cps during this time period. We also see a detection in the signal above 100 keV in the CZT detectors.

The optical counterpart (GCN 45825) at RA = 11.6142, Dec = -17.6922 implies an offset from the NuSTAR boresight of 87-deg and an offset from the geocenter of 78-deg.

Lightcurves and analysis for this GRB can be found here:
Index of /NuSTAR_Public/grbs/reports/2026/261007A (nustarsoc.caltech.edu)

Information on NuSTAR SINGS can be found here:
NuSTAR Search for INteresting Gamma-ray Signals (SINGS) (nustarsoc.caltech.edu)

NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington.

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

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