Fermi and Swift observations of the bright short GRB 090510

The bright short-hard GRB 090510 was observed by both Swift and Fermi telescopes. The study of the prompt emission by Fermi revealed an additional high-energy spectral component, the largest lower limit ever on the bulk Lorentz factor in a short GRB jet, and brought the most stringent constraint ever on linear Lorentz invariance violation models. The fast repoint and follow-up by both telescopes allowed the first multiwavelength study of a GRB afterglow from optical range to several GeV. This long-lived emission has been studied in the framework of the internal shock and external shock models.