General information
GRB 260305A is a likely long gamma-ray burst triggered by Fermi-GBM at 2026-03-05 02:41:38 UT, with subsequent reporting of likely high-energy emission in Fermi-LAT data and early optical follow-up upper limits.
Wavelength coverage
- Gamma-ray (keV–MeV): Fermi-GBM trigger and localization reported.
- High-energy gamma-ray (MeV–GeV): Likely Fermi-LAT detection with likelihood analysis and a refined position reported.
- Optical: MASTER-SAAO observations began 87 s after trigger; only upper limits reported.
No observations were mentioned in X-ray, UV, IR, radio, or spectroscopy.
Lightcurve and spectrum
- LAT: five photons within a 27.0 s interval starting at T0+14.45 s; highest-energy photon 1.6 GeV at T0+33.42 s.
- LAT likelihood (T0 to T0+100 s): photon flux above 100 MeV (9.95 +/- 5.18) x 10^-6 ph cm^-2 s^-1; photon index -1.80 +/- 0.38; TS=23.7.
- Optical: upper limits in clear/unfiltered band reaching ~18.6 mag in the first few minutes after trigger.
Redshift
What’s special vs typical
- A refined Fermi-LAT localization (68% error radius 0.22 deg) and GeV-photon cluster are reported in addition to the initial GBM trigger/localization.