Observation of blazars with the high energy SED peak in the Fermi-LAT band

After three years of scientific activity with the Large Area Telescope (LAT), the primary instrument onboard Fermi, the second catalog of the active galactic nuclei (2LAC) detected by the Fermi Large Area Telescope is now complete. It is a follow-up of the first LAT AGN catalog, (1LAC). The 2LAC includes a number of analysis refinements and additional association methods which have substantially increased the number of associations over 1LAC. Among the AGN included both in the 1LAC and in the 2LAC, those blazars that have their Spectral Energy Distribution (SED) high-energy peak centered on the Fermi-LAT band (from 20 MeV to 300 GeV) are of particular interest. The brightest of these sources have been analyzed covering a period of 22 months of Fermi LAT gamma-ray data in order to investigate their spectral features in the gamma-ray band and to characterize the temporal evolution of their gamma-ray spectra.