Long-term Study of the Light Curve of PKS 1510-089 in GeV Energies

We have analyzed data from the flat-spectrum radio quasar PKS 1510-089 collected over a period of eight years from 2008 August to 2016 December with the Fermi-LAT. We have identified several flares of this highly variable source, studied their temporal and spectral properties in detail, and compared with previous works on flares of PKS 1510-089. Five major flares and a few subflares or substructures have been identified in our study. The fastest variability time is found to be 1.30 +/- 0.18 hr between MJD 55852.063 and 55852.188, where we estimate the minimum size of the emission region to be 4.85 x 10(15) cm. In most of the flares, the spectral energy distributions are better fitted with a log-parabolic distribution compared to a simple power law or a power law with exponential cutoffs. This has strong physics implications regarding the nature of the high-energy gamma-ray emission region.