Identifying Breaks and Curvature in the Fermi Spectra of Bright Flat Spectrum Radio Quasars

TL;DR

This study investigates gamma-ray spectral features in bright FSRQs to determine emission sites, testing the double-absorber model with Fermi data, and finds inconsistent spectral breaks with model predictions, suggesting complex emission regions.

Contribution

It provides an empirical analysis of gamma-ray spectra in FSRQs, challenging the double-absorber model's predictions with observational data.

Findings

Spectral breaks are observed but do not match the predicted energies.

Spectral fits vary between epochs, indicating temporal variability.

Simple power laws are often improved by adding breaks or log-parabolas.

Abstract

Knowing the site of gamma-ray emission in AGN jets will do much for our understanding of the physics of the source. In particular, if the emission region is close to the black hole then absorption of gamma-rays with photons from the broad-line region could become significant. Such absorption is predicted to produce two specific spectral breaks in the gamma-ray spectra of Flat Spectrum Radio Quasars (FSRQs). We test this hypothesis using 3 years of Fermi observations of nine bright FSRQs. A simple power law fit to the spectrum of each source can be significantly improved by introducing a break, but the break energies are inconsistent with those predicted by the double-absorber model. In some cases the fit can be further improved by a log-parabola. In addition, by dividing the data from each source into two equal epochs we find that the best description of an object's spectrum often varies between a log-parabola and a broken power law.