GRB 260303A

General information

GRB 260303A triggered SVOM/ECLAIRs at 2026-03-03 06:01:47 UTC, with a refined localization later reported from event-by-event data. An optical afterglow candidate was reported by SVOM/COLIBRÍ and subsequently detected by SVOM/VT.

Wavelength coverage

• Gamma/X-ray (prompt; 4–120 keV): SVOM/ECLAIRs trigger and refined spectral/temporal analysis.
• Optical (r, z, VT_B, VT_R, R): Candidate detected by SVOM/COLIBRÍ (r/z) and by SVOM/VT (VT_B/VT_R); later DFOT reports an R-band upper limit.
• Near-IR (J): WINTER reports a J-band upper limit. No observations were mentioned in radio, UV, GeV/TeV gamma-rays, or spectroscopy.

Lightcurve and spectrum

• Prompt emission (SVOM/ECLAIRs): single-peak lightcurve; duration ~14.5 s (from T0-19.5 s to T0-5 s) in 4–120 keV.
• Prompt spectrum (SVOM/ECLAIRs): power-law photon index 1.67 (+0.14/-0.13); fluence (4–120 keV) (1.19 +0.11/-0.20)e-6 erg/cm^2; photon flux 2.73 (+0.16/-0.31) ph/cm^2/s.
• Optical evolution: SVOM/COLIBRÍ reports the source rises then falls in both r and z; SVOM/VT reports fading between ~10.4 min and ~47.5 min post-trigger in VT_B and VT_R.

Redshift

What’s special vs typical