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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: GROWTH-India Telescope optical observations
GCN Circulars —

GCN Circular 45841
GRB 261007A: GROWTH-India Telescope optical observations
From: Aditya Pawan Saikia at IIT Bombay
Issued: 2026-10-07 17:21 UTC
Type: GRB, Optical Transient

R. Arya (IITB), A. Sarkar (IITB), V. Vijaykumar (IITB), S. Patil (IITB), A.P. Saikia (IITB), V. Swain (IITB), T. Mohan (IITB), V. Bhalerao (IITB), G.C. Anupama (IIA), S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team:

We observed the field of GRB 261007A detected by SVOM (SVOM mission Team, GCN 45824), with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2026-10-07 15:05:35, i.e., 9.34 hours after the trigger, and obtained multiple exposures in the SDSS r' and g' filters. We detect the optical counterpart in our images at the position reported by Zheng et al., GCN 45825. The photometric results are as follows:

| MJD (mid) | Filter | tmid-t0 (hours) | Exposure Time (sec) | Magnitude (AB) |
| -------------- | ------ | --------------- | ------------------- | ---------------- |
| 61320.688 | r' | 9.603 | 4x300 | 20.11 +/- 0.06 |
| 61320.686 | g' | 10.389 | 3x300 | 20.56 +/- 0.08 |

The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction.

Our results are consistent with other optical observations (An et al., GCN 45840, Saccardi et al., GCN 45829 and GCN 45837, Shi. et all, GCN 45838, and Mohan.et al. GCN 45832)

The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at GROWTH-India (sites.google.com).

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

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