Ackermann, M.M.AckermannAjello, M.M.AjelloBaldini, L.L.BaldiniCutini, SaraSaraCutiniGasparrini, DarioDarioGasparriniGiommi, PaoloPaoloGiommiTosti, G.G.Tosti2020-09-172020-09-172010-07-01https://hdl.handle.net/20.500.13025/1793The Astrophysical Journal Letters, Volume 717, Issue 2, pp. L127-L132 (2010).The Fermi observatory is advancing our knowledge of gamma-ray bursts (GRBs) through pioneering observations at high energies, covering more than seven decades in energy with the two on-board detectors, the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM). Here, we report on the observation of the long GRB 090217A which triggered the GBM and has been detected by the LAT with a significance greater than 9sigma. We present the GBM and LAT observations and on-ground analyses, including the time-resolved spectra and the study of the temporal profile from 8 keV up to ~1 GeV. All spectra are well reproduced by a Band model. We compare these observations to the first two LAT-detected, long bursts GRB 080825C and GRB 080916C. These bursts were found to have time-dependent spectra and exhibited a delayed onset of the high-energy emission, which are not observed in the case of GRB 090217A. We discuss some theoretical implications for the high-energy emission of GRBs.gamma-ray burst individual GRB090217A10.1088/2041-8205/717/2/L127http://adsabs.harvard.edu/abs/2010ApJ...717L.127A2010ApJ...717L.127A