The Statistical Analysis of GeV Spectral Breaks in Bright Gamma-Ray Flat-spectrum Radio Quasars

Abstract

We present the statistical 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 data of the Large Area Telescope on board Fermi Gamma-Ray Space Telescope. We have fitted the 15 yr average gamma-ray spectra of 755 FSRQs by using both the broken power law (BPL) and logarithmic parabola (LP) models, and obtained 87 bright gamma-ray FSRQs with their integrated photon fluxes greater than 2.16 × 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 the 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 2.90 ± 1.92 GeV in the rest frame, and the observed change in photon index is Δ γ = 0.45 ± 0.19, which is consistent with the expected value for a cooling break of electrons scattering seed photons.

Keywords

• Active galactic nuclei
• Gamma-ray sources
• Blazars
• Flat-spectrum radio quasars