General information
GRB 260822A was triggered by SVOM/ECLAIRs at 2026-08-22T16:50:36 UTC and localized to RA=2.4240 deg, Dec=1.3876 deg with a 90% confidence radius of 9.15 arcmin. SVOM/ECLAIRs classified it as a short burst, with independent SVOM/GRM detection and extensive follow-up but no confirmed afterglow.
Wavelength coverage
- Gamma-ray: SVOM/ECLAIRs detected the burst with best SNR 8.62 and later reported T90(4-120 keV)=0.18 ± 0.05 s, no obvious extended emission, photon index -1.0 ± 0.1, photon flux 6.9 +0.3/-1.4 photons/cm^2/s, and fluence (6.5 ± 0.9)e-8 erg/cm^2; SVOM/GRM also triggered on a 0.10 s timescale with SNR 6.20.
- X-ray: SVOM/MXT was in Earth occultation at trigger time; Einstein Probe/FXT observed about 19.2 hr later and detected several uncataloged X-ray sources with 0.5-10 keV fluxes from 2.1891e-14 to 1.2304e-13 erg cm^-2 s^-1, but no significant variability or association was identified.
- Optical: GOTO, GROWTH-India, LCO, SVOM/COLIBRÍ, and SVOM/VT observed the field; tentative optical detections were later not confirmed as a GRB afterglow, with the COLIBRÍ/VT candidate identified as an unrelated pre-existing type-Ia supernova and the GOTO source retracted as consistent with minor planet 2016 CP289.
- Near-infrared: PRIME observed in J and H at about 5.5 hr and 30 hr and found no significant varying sources, with limits including J > 21.4 AB and H > 21.2 AB at epoch 1 and J > 21.7 AB and H > 21.3 AB at epoch 2.
- Spectroscopy: VLT/MUSE observed the candidate source and found broad supernova-like undulations, with nearby galaxies at z=0.290 and z=0.296.
Bands with no observations mentioned: radio, submillimeter, neutrino, and gravitational-wave.
Lightcurve and spectrum
- SVOM/ECLAIRs initially reported a single narrow peak lasting about 100 ms, while the later ECLAIRs analysis described a multi-peaked light curve with T90(4-120 keV)=0.18 ± 0.05 s.
- SVOM/ECLAIRs detected no obvious extended emission.
- SVOM/ECLAIRs fitted the 5-120 keV time-averaged spectrum from T0+0.637 s to T0+0.817 s with a power law of photon index -1.0 ± 0.1.
- SVOM/GRM observed a single narrow peak lasting about 100 ms.
- Einstein Probe/FXT reported no significant flux variability from the detected X-ray sources.
Redshift
VLT/MUSE measured nearby galaxies at z=0.290 and z=0.296 from Halpha, [N II], [O III], and Hbeta emission lines. VLT/MUSE spectroscopy of the candidate source showed broad supernova-like undulations, and SNID template matching gave a type-Ia SN post-peak at z=0.291 ± 0.010; VLT/MUSE and Pan-STARRS data supported that this source was unrelated to GRB 260822A.
What’s special vs typical
The burst is notably short, with T90 about 0.18 s and no obvious extended emission. However, despite broad follow-up, the reported optical candidate was not a GRB afterglow but an unrelated pre-existing type-Ia supernova, so the event remains a short GRB without a confirmed counterpart in the provided circulars.