General information
GRB 260818B was triggered by SVOM/ECLAIRs and was also detected by SVOM/GRM and HXMT. SVOM/VT performed optical ToO observations beginning about 3.4 hr after trigger, with additional epochs at 1.02 d and 7.5 d.
Wavelength coverage
- Gamma-ray: triggered by SVOM/ECLAIRs and also detected by SVOM/GRM and HXMT.
- Optical: SVOM/VT observed in VT_B and VT_R; no credible candidate was found in stacked images, with typical 5-sigma limits of 23.0 AB mag in both channels.
- Optical: LCO, SVOM/COLIBRÍ, NOT, and SVOM-CGFT are reported as consistent with the non-detection.
- Optical: SVOM/VT notes a possible brightening trend for VLA source S10 in VT_R, but cannot confirm the nearby COLIBRÍ candidate because of blending and limited resolution.
- Radio: VLA radio sources are mentioned, including S10.
- X-ray: Einstein Probe X-ray sources are mentioned, and S10 is spatially coincident with EPF_J025955.0+072535.
No observations are mentioned in gravitational waves, neutrinos, or FRB-like radio-burst searches.
Lightcurve and spectrum
- Earliest SVOM/VT observation began at 2026-08-18T23:33:18 UTC, about 3.4 hr post trigger, in VT_B and VT_R simultaneously.
- Additional SVOM/VT ToO observations occurred at 1.02 d and 7.5 d post trigger.
- Typical stacked-image 5-sigma upper limits are 23.0 AB mag in both VT_B and VT_R.
- VLA source S10 is reported at VT_R = 22.2±0.3 mag at 5.1 hr and VT_R = 21.7±0.2 mag at day 7, suggesting a possible positive trend.
Redshift
What’s special vs typical
The main point of interest is the tentative optical brightening of S10, a VLA radio source spatially coincident with an Einstein Probe X-ray source, near a separately proposed COLIBRÍ optical candidate. However, the association is not confirmed in this circular.