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Transient Alerts » in reply to GRB 261011A — GRB, X-ray Transient

In plain words Notable

On 11 October 2026 two satellites, SVOM and Swift, caught a long gamma-ray burst (a brief flash of high-energy light from a distant exploding star) in the southern sky. It lasted roughly a minute or more, depending on the instrument. Within minutes, telescopes around the world saw a fading visible-light and X-ray afterglow at the same spot. Two large telescopes measured the distance from the light's fingerprints: the burst happened at redshift 2.407, meaning the light left roughly 11 billion years ago. The afterglow faded below detection within about a day, and no host galaxy has been clearly detected. It is most likely an ordinary long burst from the collapse of a massive star. Swift's first report of an unusual light curve was withdrawn after a closer look showed that part of it came from noisy detectors.

How unusual is it? Most gamma-ray bursts have no measured distance, but this one has a confirmed redshift (2.407) from two independent telescopes plus a bright afterglow seen in many wavelengths; otherwise its properties look typical, and the initially reported oddity turned out to be instrumental noise.

Written by an AI model (claude-sonnet-5-5) from the official reports in this thread, and rewritten as new reports arrived (version 9); last updated . It may contain mistakes: the reports themselves are the authority.

GRB 261011A: REM optical/NIR observations
GCN Circulars —

GCN Circular 45926
GRB 261011A: REM optical/NIR observations
From: Riccardo Brivio at INAF-OAB
Issued: 2026-10-12 17:05 UTC
Type: GRB, Optical Transient

R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team:

We observed the field of GRB 261011A, detected by Swift/BAT (Huang et al., GCN 45895; Cenko et al., GCN 45896) and SVOM/ECLAIRs with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile).
The observations were carried out in the g, r, i, z, K bands, started on 2026-10-12 at 01:30:16 UT (i.e. 11.7 hr after the burst) and lasted for about 2.0 hr.

From preliminary photometry, we do not detect the optical/NIR counterpart (Cenko et al., GCN 45896; O'Neill et al., GCN 45897; Fu et al., GCN 45898; Izzo et al., GCN 45899; Wu et al., GCN 45900; Yin et al., GCN 45901; Shi et al., GCN 45903; Aryan et al., GCN 45904; Arya et al., GCN 45907; Izzo et al., GCN 45909; Huang et al., GCN 45913; Bochenek et al., GCN 45914; Li et al., GCN 45915; Zhao et al., GCN 45916; Takahashi et al., GCN 45917; Monsalvel et al., GCN 45920; Cheng et al., GCN 45922) down to the following 3sigma limits:


r > 20.6 (AB; calibrated against the PanSTARRS catalogue),
at a mid-time of 12.1 hr after the trigger;

K > 14.2 (Vega; calibrated against the 2MASS catalogue),
at a mid-time of 11.8 hr after the trigger.

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

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