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

TL;DR

This study analyzes the spectral breaks in bright gamma-ray FSRQs using 15 years of Fermi data, revealing common spectral features and their implications for electron cooling processes.

Contribution

First comprehensive statistical analysis of GeV spectral breaks in bright gamma-ray FSRQs using extensive Fermi-LAT data and spectral modeling.

Findings

Spectral breaks are located at 2.90±1.92 GeV in the rest frame.

Photon index change across breaks is 0.45±0.19.

Both BPL and LP models fit the data similarly well.

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.