Frederic R. Piron
We present the observations of the longest Gamma-Ray Burst (GRB) high-energy afterglows by the Fermi Large Area Telescope (LAT). This includes the detection of the two long GRB 090323 and GRB 090328, which also triggered the Fermi Gamma-Ray Burst Monitor (GBM). In both cases, an Autonomous Repoint Request allowed the afterglow emission to be monitored for 5 hours, and a significant high-energy signal was detected in the LAT up to several kilo-seconds. We will report on the .me-resolved GBM and LAT joint spectroscopy in the prompt phase, and on the temporal study of the late extended emission in the LAT. Along with the redshift measurements for both bursts (z=3.57 and z = 0.736, respectively), these observations give new insight in the energetics and emission mechanisms in the prompt and afterglow phases.