General information
GRB 260616A is a likely long GRB detected at about 2026-06-16 03:21:54 UT by Fermi-GBM and independently seen by many high-energy instruments. The best reported LAT position is RA = 93.53 deg, Dec = -32.07 deg with a 0.54 deg statistical error radius.
Wavelength coverage
- Gamma-ray / hard X-ray: Fermi-GBM, Fermi-LAT, GECAM-B, Konus-Wind, Insight-HXMT, NuSTAR shields, SVOM/GRM, AstroSat CZTI/Veto, and Avion/DeCoR reported detections of the prompt emission.
- High-energy gamma-ray: Fermi-LAT detected emission above 100 MeV from 500-3000 s after the GBM trigger, with a highest-energy photon of 724 MeV at 1690 s.
Bands with no observations mentioned: optical, near-infrared, ultraviolet, soft X-ray afterglow, radio, neutrino, and gravitational-wave.
Lightcurve and spectrum
- Fermi-GBM reports T90 about 69 s in 50-300 keV, a Band spectrum with Epeak = 246 +/- 1 keV, alpha = -0.63 +/- 0.01, beta = -2.00 +/- 0.01, fluence (1.22 +/- 0.02)e-4 erg/cm^2 in 10-1000 keV, and 1-s peak photon flux 16.9 +/- 0.4 ph/s/cm^2.
- Fermi-LAT reports significant high-energy emission with photon flux above 100 MeV of (1.8 +/- 0.6)e-6 ph/cm2/s from 500-3000 s, photon index -2.4 +/- 0.4, and a highest-energy photon of 724 MeV.
- GECAM-B reports multiple pulses, T90 = 117 +/- 3 s, Epeak = 679 +141/-121 keV, and fluence (2.02 +0.05/-0.06)e-4 erg/cm^2 in 10-1000 keV.
- Konus-Wind reports a bright multipeaked pulse, total duration about 292 s, a possible weaker precursor around T0-422 s, emission up to about 4 MeV, fluence 2.77 +/- 0.09e-4 erg/cm2, and Band Epeak = 295 +11/-10 keV for the time-averaged spectrum.
- Insight-HXMT reports dense spikes with T90 = 76.0 +4.5/-4.0 s, 1-s peak rate 5435 counts/s, and total counts 178317.
- NuSTAR SINGS reports prompt emission lasting about 100 s in the CsI shields, with peak count rate about 1500 cps over a baseline of about 1000 cps, and no evidence above 100 keV in the CZT detectors.
- SVOM/GRM reports multiple pulses with T90 = 143 +5/-4 s, Epeak = 573 +61/-52 keV, fluence (2.14 +/- 0.03)e-4 erg/cm^2, and 1-s flux (4.48 +0.15/-0.14)e-6 erg/cm^2/s.
- AstroSat CZTI reports multiple peaks, T90 = 113 +/- 5 s in CZT and 112 +3/-4 s in Veto, with 2989 preliminary Compton events associated with the burst.
- Avion reports multiple peaks, fluence about 7.5e-6 erg/cm^2 in 40-500 keV, maximum flux about 4.5 phot/(cm^2*s), and T90 about 80 s.
Redshift
What’s special vs typical
GRB 260616A is more notable than a routine single-instrument GRB because it was bright, long, detected by Fermi-LAT at >100 MeV, and independently recorded by a large set of prompt high-energy instruments. Konus-Wind also reports a possible precursor hundreds of seconds before the main trigger.