The Statistic Analysis of GeV Spectral Breaks in Bright Gamma-Ray FSRQs

Abstract

We present the statistic results of GeV spectral breaks of bright gamma-ray flat-spectrum radio quasars (FSRQs) in the energy range of 0.1-10 GeV based on New Pass 8 date of the Large Area Telescope abroad on Fermi Gamma-ray Space Telescope. We have fitted the 15-year average gamma-ray spectra of 755 FSRQs by using both a broken power-law (BPL) and the Logarithmic Parabolas (LP) models, and obtained 87 bright gamma-ray FSRQs with their integrated photon fluxes greater than $2.16\times 10^{-8}$ cm$^{-2}$ s$^{-1}$. From our results, the FSRQ population shows similar preferences for both the BPL and LP models in gamma-ray spectral fitting and clustering analysis suggests that BPL-preferred and LP-preferred FSRQs belong to the same category. Our results indicate that GeV spectral breaks in bright gamma-ray FSRQs are located at $\rm 2.90\pm1.92$ GeV in the rest frame, and the observed change in photon index is $\rm \Delta \gamma =0.45 \pm 0.19$, which is consistent with the expected value for a cooling break of electrons scattering seed photons.