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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: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at McDonald Observatory
GCN Circulars —

GCN Circular 45844
GRB 261007A / EP261007a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at McDonald Observatory
From: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias
Issued: 2026-10-07 21:42 UTC
Type: GRB, X-ray Transient, Afterglow, Optical Transient

E. Ruiz-Laguna, S. Abad Gómez, K.N. Alvez Báez, G. de la Mata Núñez, J. Díaz-Miguel Font, A. Fernández-Roselló, L. García Rodríguez, S. M. Holtham, R. Jiménez Rioja, H. Morín-González, L. Ortega-Barcenilla, C. Pasamontes-Duarte, M. Ríos-Jiménez, S.J. Riquelme-Salinas, L. Rodríguez-Torres, A. Rosendo Pato, I. Ruiz-Pérez, D. Zazo-Callejas (all ULL), S. R. Berlanas (IAC and ULL),
and I. Pérez-Fournon (IAC and ULL)

We report on observations of the optical counterpart of GRB 261007A detected by SVOM/ECLAIRs and SVOM/GRM (Goto et al., GCN 45824), Einstein Probe WXT and FXT (EP261007a, Wen et al., GCN 45828), and Fermi GBM (Malacaria, GCN 45830).

We observed the field of GRB 261007A / EP261007a with a Las Cumbres Observatory (LCO) 40-cm telescope
located at the LCO node at McDonald Observatory, Texas, with 180-sec exposures in each of the SDSS g´, r´, and i' filters. The first observation started on 2026-10-07 at 07:07:24 UT, about 1.4225 hr after the SVOM trigger. The optical counterpart first detected with KAIT by Zheng et al. (GCN 45825) is clearly detected in all bands. We measure the following AB magnitudes, calibrated against PanSTARRS-1 DR2 stars and not corrected for Galactic extinction:

Date (UT, mid-time) | filter | mag | error | mid t - t0 (hr)
-----------------------------------------------------------------------
2026-10-07T07:08:54 | g' | 18.59 | 0.06 | 1.4475
2026-10-07T07:12:04 | r' | 18.33 | 0.08 | 1.5003
2026-10-07T07:15:11 | i' | 18.10 | 0.16 | 1.5522

Our results are consistent with other optical and near-IR detections: Saccardi et al. (GCN 45829, spectroscopic redshift of 2.101), Mohan et al. (GCN 45832), Saccardi et al. (GCN 45837), Shi et al. (GCN 45838), An et al. (GCN 45840), Arya et al. (GCN 45841), Rehemtulla et al. (ZTF26abzxgsr, GCN 45843), and Fracile et al. (AT 2026aepi, TNS Astronomical Transient Report No. 327228).

Based on observations made with the Las Cumbres Observatory’s education network telescopes that were upgraded through generous support from the Gordon and Betty Moore Foundation (LCO program IAC2026B-010).

These observations are part of a course in Astrophysical Techniques of the Master in Astrophysics of the Astrophysics Department of the University of La Laguna in collaboration with the Instituto de Astrofísica de Canarias (La Laguna, Tenerife, Canary Islands, Spain).

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

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