GRB 260619A

General information

GRB 260619A was detected by SVOM/ECLAIRs at 2026-06-19T02:12:40 UTC as a faint image-trigger event, and later circulars report a repeatedly detected optical counterpart/afterglow candidate. The ECLAIRs localization was RA 359.0538 deg, Dec -15.3917 deg with a 90% confidence radius of 11.33 arcmin.

Wavelength coverage

• Gamma-ray: SVOM/ECLAIRs detected a faint burst with SNR 6.90 in 8-50 keV, duration about 40 s, and a refined 5-120 keV spectrum best fit by a blackbody with kT = 6.6 -1.3/+1.6 keV.
• Optical: Kilonova-Catcher reported no uncatalogued optical source to r > 20.3 at 4.29 h; SVOM/COLIBRI, SVOM/VT, TRT, and NOT later reported detections of the optical candidate/afterglow in r, z, VT_B, VT_R, and i bands. Bands with no observations mentioned: X-ray afterglow, ultraviolet, infrared beyond z/VT_R optical-red coverage, radio, millimeter/submillimeter, gravitational waves, and neutrinos.

Lightcurve and spectrum

• The gamma-ray light curve is described as a faint single peak lasting about 40 s in the 8-50 keV band.
• The time-averaged ECLAIRs spectrum from T0-40.96 s to T0 is best fit by a blackbody model with kT = 6.6 -1.3/+1.6 keV.
• The 4-120 keV fluence is (2.03 +/- 0.63)e-7 erg/cm2 and the 4-120 keV photon flux is (2.02 +/- 0.33)e-1 ph/cm2/s.
• SVOM/COLIBRI measured the uncatalogued source at r = 22.13 +/- 0.05 and z = 21.91 +/- 0.14 at 7.62-9.01 h after trigger.
• SVOM/VT measured VT_B = 22.56 +/- 0.15 and VT_R = 22.63 +/- 0.18 at about 6.1 h after trigger.
• TRT measured r ~ 21.4 at a median time of 3.95 h post-trigger.
• NOT measured i = 22.26 +/- 0.08 at 1.114 d and noted little evolution compared with earlier flux values.
• Later SVOM/VT observations at 21.24 d measured VT_B = 23.9 +/- 0.3 and VT_R = 22.4 +/- 0.2, described as about 1 mag fading in VT_B while VT_R remained stable.

Redshift

What’s special vs typical

• The burst was faint and initially below the SVOM slew threshold, with possible contamination noted from high proper motion stars in the ECLAIRs error box.
• Despite the weak initial trigger, multiple optical facilities detected the same candidate, and later data show color-dependent evolution with VT_B fading while VT_R remained stable.
• The refined gamma-ray spectrum is reported as blackbody-like, and the NOT circular explicitly noted little optical brightness evolution compared with earlier measurements.