General information
SVOM/ECLAIRs triggered on the possible gamma-ray burst GRB 260831B (sb26083106) at 2026-08-31T18:36:12 UTC. Follow-up observations in X-ray and optical bands did not find an uncatalogued counterpart, and the field includes the known classical nova V* GK Per.
Wavelength coverage
- Gamma-ray: SVOM/ECLAIRs detected the event in the 8-50 keV band with an image-trigger sequence of 5 alerts.
- X-ray: SVOM/MXT reported no source in a >10 min exposure; EP-FXT reported no uncatalogued source with an upper limit of about 2 x 10^-13 erg/s/cm^2.
- Optical: LCO, SVOM/VT, and GWAC-F60A/B found no uncatalogued source; VT and GWAC both reported variability from the known nova V* GK Per.
Bands with no observations mentioned: none.
Lightcurve and spectrum
- SVOM/ECLAIRs light curve was featureless.
- Best image-trigger alert had SNR 9.11 in the 8-50 keV band over a 655.36 s window.
- SVOM/MXT: no source detected during a >10 min exposure.
- LCO: no new source detected; limits r > 21.5 AB and z > 20.2 AB.
- SVOM/VT: no uncatalogued source detected down to about 22.5 mag AB in both VT_B and VT_R.
- GWAC-F60A/B: no credible uncatalogued candidates; limit R > 18.6 mag.
- V* GK Per showed optical variability of about 0.2 mag in SVOM/VT, with consistent variation seen by GWAC-F60A/B.
Redshift
What’s special vs typical
The main unusual feature is the presence of the known nova V* GK Per inside the ECLAIRs error circle, which showed variability during the follow-up campaign. Otherwise the burst remains an unconfirmed GRB candidate with only upper limits and no detected afterglow.