General information
GRB 260618C was detected by SVOM/ECLAIRs through an on-ground search at 2026-06-18T04:02:26.6 UTC, localized to RA = 294.933 deg and Dec = -65.710 deg with a 90% confidence radius of 10.7 arcmin. The circular describes it as a possible burst and notes no bright catalogued X-ray sources in the error box.
Wavelength coverage
- High-energy / soft gamma-ray / X-ray: SVOM/ECLAIRs detected the transient in several energy ranges and timescales, with the best detection in 4-20 keV.
- X-ray: No bright catalogued X-ray sources were found in the error box; SVOM/MXT follow-up was requested but no results are reported in the circular.
- Optical: SVOM/VT follow-up was requested but no observations are reported in the circular.
No radio, infrared, ultraviolet, gravitational-wave, or neutrino observations are mentioned.
Lightcurve and spectrum
- The burst has a single peak structure.
- T90 = 6 +/- 1 s in the 4-20 keV energy band.
- Best detection: signal-to-noise ratio 8.6 in 4-20 keV over 7 s starting at T0-7 s.
- Time-averaged spectrum from T0-7 s to T0 in 5-50 keV is best fit by a blackbody with kT = 3.65 +0.47/-0.42 keV.
- The 4-120 keV fluence is (8.3 +0.7/-2.4) e-8 erg/cm^2, and the 4-120 keV photon flux is 0.65 +0.04/-0.15 ph/cm^2/s.
- Broken power-law and cutoff power-law models can also fit the spectrum, but their parameters cannot be constrained due to faintness.
Redshift
What’s special vs typical
- The event is reported as very soft; the authors state that if it is a GRB, it should probably be classified as an X-ray flash.