GRB 260829A

General information

GRB 260829A is a likely long gamma-ray burst first triggered by Fermi/GBM at 2026-08-29 06:08:09 UT and subsequently reported by multiple high-energy missions. The Fermi/GBM final real-time localization is RA 242.3 deg, Dec -34.6 deg with 1.0 deg statistical uncertainty.

Wavelength coverage

• Gamma-ray / hard X-ray: Fermi/GBM detected and localized the burst; BALROG provided an independent GBM-based localization; GECAM-B, Konus-Wind, AstroSat/CZTI, and SVOM/GRM detected the prompt emission; IPN triangulation used Fermi, Konus-Wind, GECAM-B, and Mars-Odyssey/HEND.
• High-energy field-of-view note: SVOM/ECLAIRs did not cover the Fermi/GBM position because it was about 134 deg from the SVOM optical axis. No optical, infrared, ultraviolet, X-ray afterglow, radio, neutrino, or gravitational-wave observations are mentioned.

Lightcurve and spectrum

• Fermi/GBM: prompt emission followed by a bright peak; T90 about 26.4 s in 50-300 keV. Time-averaged spectrum from T0+18 to T0+34 s is fit by a Band function with Epeak = 260 +/- 10 keV, alpha = -0.66 +/- 0.04, beta = -2.17 +/- 0.08; fluence is (1.91 +/- 0.03)e-5 erg/cm^2 in 10-1000 keV, and 1-s peak photon flux is 19.1 +/- 0.3 ph/s/cm^2.
• GECAM-B: mainly a single pulse with T90 = 47.0 +/- 4.0 s in about 70-6000 keV. Spectrum from T0+16 to T0+32 s is fit by a cutoff power law with index -1.15 +0.18/-0.15 and Epeak = 466 +138/-94 keV; fluence is (2.31 +0.13/-0.16)e-5 erg/cm^2 in 10-1000 keV.
• AstroSat/CZTI: Veto detector detected the source in 100-500 keV, peaking at 2026-08-29 06:08:31.7 UTC, with peak count rate 614 (+58, -62) counts/s above background and T90 = 13.1 (+5.3, -6.5) s. CZT detectors detected it in 20-200 keV with multiple peaks and strongest peak at 06:08:30.7 UTC.
• SVOM/GRM: multi-pulse light curve with T90 = 28 +3/-5 s in 15-5000 keV. Spectrum from T0-25 to T0+13 s is fit by a power law with index -2.11 +0.07/-0.08 and fluence (6.197 +0.467/-0.406)e-5 erg/cm^2 in 10-1000 keV.
• Konus-Wind: initial weak emission starting about T0-21.3 s followed by a brighter multi-peaked structure; total duration about 34.8 s and emission up to about 4 MeV. Total fluence is 2.05(-0.09,+0.10)e-5 erg/cm^2 and 64-ms peak flux is 8.44(-0.91,+0.92)e-6 erg/cm^2/s in 20 keV-10 MeV; time-averaged spectrum has alpha = -0.94 +/- 0.09 and Ep = 330(-24,+28) keV.

Redshift

What’s special vs typical

• The event has unusually broad prompt gamma-ray coverage across several spacecraft and an IPN triangulation, making the prompt properties comparatively well documented.
• Within the supplied circulars, it otherwise appears to be a conventional long GRB: no afterglow, host, redshift, or multi-messenger association is reported.