The Fermi LAT observations of the Gamma Ray Bursts

After 15 months of science operation, the Fermi Gamma-ray Burst Monitor has triggered on more than 300 GRBs, including 12 detections above 100 MeV by the Large Area Telescope (LAT). With the Fermi/LAT high-energy photons up to ∼30 GeV (the highest energy ever for GRBs) during the prompt emission were detected as well as long lasting high-energy emission of several kilo-seconds after the trigger time. Here, we present the common properties of the LAT detected bursts and their implications in terms of GRB jet astrophysics. Beyond a better understanding of GRB emission mechanisms, these observations also help to address more fundamental physics issues and constrain some theoretical scenarios for the UHECRs sources.