Fermi LAT and the Observation of Flares in Extragalactic Sources

English The directional coincidence, within 6 arcminutes, between the neutrino detected by IceCube and an extragalactic source with increased activity, observed at GeV energies by the LAT detector on board the Fermi spacecraft, requires an in-depth study of the direction and time distribution of gamma-ray active sources, in order to understand what the probability of a random coincidence could be. In this thesis, we aim to prepare a catalog of «flares» (intense and sudden increases in luminosity) of some sources detected by the Large Area Telescope on board the Fermi spacecraft. The catalog should indeed become the basis to understand what the probability to have a directional coincidence with high-energy neutrinos would be, with important consequences on acceleration models powering active galactic nuclei.