Short and long term flux variability of the BL Lacertae object 1ES 2200+420, in the MeV - GeV range

Blazars are a class of Active Galactic Nuclei (AGN) that exhibit variable flux states across the electromagnetic spectrum, from radio to TeV. Current measurements show that the MeV-GeV flux of a Blazar could have a variability time scale as small as few hours or as long as several months. In this talk I will report the MeV-GeV flux variability patterns of the BL Lacertae object (1ES 2200+420). The data has been obtained from the Fermi-LAT archival database, and analysed using the recently released Pass 8 Fermi Science Tools. The cross correlations between MeV-GeV flux and KeV flux observed by Swift-XRT will also be reported, which is an important measurement to constraint the Synchrotron models.