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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 detected on 7 October 2026 by SVOM, a China-France satellite, and by several other space telescopes, including Fermi, NuSTAR, AstroSat and the Einstein Probe. It came from a spot in the southern sky and lasted about 23 seconds, which makes it a long gamma-ray burst, the kind usually linked to the death of a massive star. Within minutes, ground telescopes found a fading optical afterglow, and Swift later detected an X-ray afterglow at the same position. A large telescope in Chile (the VLT) measured the distance from the afterglow's light: the explosion happened about 2.1 in redshift, meaning the light left roughly 10 billion years ago. The afterglow was bright at first, around magnitude 15 within two minutes, and had faded to about magnitude 21 a day later, as expected.

How unusual is it? A spectroscopic redshift (z = 2.101) and a bright optical afterglow caught within minutes and followed in X-rays by many telescopes make this better studied than most of the few hundred bursts seen each year, but the burst itself looks like a typical long gamma-ray burst, not a record-breaker.

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

GRB 261007A / EP261007a: SVOM/VT optical observations
GCN Circulars —

GCN Circular 45851
GRB 261007A / EP261007a: SVOM/VT optical observations
From: Huali Li at at NAOC, SVOM
Issued: 2026-10-08 07:33 UTC
Type: GRB, X-ray Transient, Optical Transient

H. L. Li, Y. N. Ma, L. P. Xin, C. Wu, Y. L. Qiu, Z. H. Yao, J. R. Xu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA/Irfu), W. L. Zhang (PMO), X. Tian (GXU) report on behalf of the SVOM/VT team.

SVOM/VT performed observations with automatic slew to the field of GRB 261007A triggered by SVOM/ECLAIRs (sb26100701, Goto et al., GCN 45824). This burst was also detected by SVOM/GRM (Goto et al., GCN 45824), Fermi-GBM (Malacaria et al., GCN 45830) and Einstein Probe as EP261007a (Wen et al., GCN 45828). The current available VT data started at 2026-10-07T13:00:15 UTC, approximately 7.317 hr post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously.

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) with the redshift z=2.101 (Saccardi et al., GCN 45829) was clearly detected in both channels.

The preliminary measurements are given in AB magnitudes and are not corrected for Galactic extinction:

Mid time | Band | Exposure Time | Brightness
15.65 hr VT_B 21*70 s 21.4+/-0.1 mag
15.66 hr VT_R 16*70 s 21.0+/-0.1 mag

The light curves show fading behavior in both channels with a slope of -1.4 for our available data spanning 7.6 hr to 15.7 hr.

The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.

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

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