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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: Optical follow-up observations with Kinder
GCN Circulars —

GCN Circular 45855
GRB 261007A/EP261007a: Optical follow-up observations with Kinder
From: Amar Aryan at National Central University, Institute of Astronomy (NCUIA)
Issued: 2026-10-08 09:52 UTC
Type: GRB, X-ray Transient, Optical Transient

Z.-Y. Chen, A. Aryan, T.-W. Chen, C.-S. Lin (all NCU), A. K. H. Kong (NTHU), S. J. Smartt, J. H. Gillanders (both Oxford), S. Yang (HNAS), A. Sankar.K, K. N.-T. Ho, A. Dutta, M.-H. Lee, Y.-H. Lee, Y.-C. Pan, C.-C. Ngeow, C.-H. Lai, H.-C. Lin, H.-Y. Hsiao, W.-J. Hou, J.-K. Guo (all NCU), Z. N. Wang, D. C. Qiang, L. L. Fan (all HNAS), Y. J. Yang (NYUAD), H.-W. Lin (UMich), K. W. Smith, H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, C. Angus, A. Aamer (all QUB), T. Moore (STScI), A. Schultz and M. Huber (both IfA, Hawaii) report:


As part of the Kinder collaboration (Chen et al. 2025, ApJ, 983, 86, doi:10.3847/1538-4357/adb428), we conducted follow-up observations of the Gamma-ray Burst, GRB 261007A / fast X-ray transient EP261007a (Goto et al., GCN 45824; Malacaria et al., GCN 45830; Wen et al., GCN 45828). Imaging was acquired in the r-band using the 1m LOT and in the i-band using the 40cm SLT. The first LOT epoch of observations in r-band started at 14:01 UTC on the 07th of October 2026 (MJD 61320.5813), 21.35 hr after the EP-WXT detection.

We utilized the Python-based package AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform template subtraction with the DESI Legacy Survey (Dey et al. 2019, AJ 157, 168) DR10 images using the 'SFFT' (Hu et al. 2022, ApJ, 936, 157) algorithm on individual frames. The optical counterpart (Zheng et al., GCN 45825; 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., GCN 45843; Ruiz-Laguna et al., GCN 45844; Angulo et al., GCN 45848; Li et al., GCN 45851) with the redshift z=2.101 (Saccardi et al., GCN 45829) was clearly detected in both bands.

Moreover, we further used AutoPhOT to perform PSF photometry. The details of the observations and the measured photometry from the first frame of each band are as follows:

Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | Seeing | Airmass
LOT | r | 61320.5813 | 8.25 | 300 * 1 | 20.01 +/- 0.04 | 1".9 | 1.49
SLT | i | 61320.5841 | 8.32 | 300 * 1 | 19.9 +/- 0.1 | 2".1 | 1.46



The presented magnitudes are calibrated using the field stars from the ATLAS-RefCat2 catalog from MAST (Tonry J. L. et al. 2018, ApJ, 867, 105) and are not corrected for the expected Galactic foreground extinction of A_r = 0.08 mag and A_i = 0.06 mag in the direction of the transient (Schlafly & Finkbeiner 2011). The methodology, details on the Lulin observatory telescopes, and a compilation of our optical follow-up campaign for FXTs discovered within the first year of operation of the Einstein-Probe mission are presented in Aryan et al. 2025, ApJS, 281, 20, doi:10.3847/1538-4365/adfc69.

Every one of the gamma-ray bursts GCN reports is posted here.
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