Identifying Breaks and Curvature in the Fermi Spectra of Bright FSRQs and Constraining the Emission Region

TL;DR

This study investigates gamma-ray spectra of bright FSRQs, identifying spectral breaks and curvature, and examines their implications for the location of the emission region near the black hole.

Contribution

It provides observational evidence of spectral deviations and variability in FSRQs, challenging existing models of gamma-ray absorption near the black hole.

Findings

Spectral breaks are observed but not at predicted energies.

Log-parabola fits often outperform broken power laws.

Spectral shapes vary over time in many objects.

Abstract

Deviation of the gamma-ray energy spectra of Flat Spectrum Radio Quasars (FSRQs) from a simple power law has been previously observed but the cause of this remains unidentified. If the gamma-ray emission region is close to the central black hole then absorption of gamma-rays with photons from the broad line region is predicted to produce two spectral breaks in the gamma-ray spectra at fixed energies. We examine 9 bright FSRQs for evidence of breaks and curvature. Although we confirm deviation from a simple power law, break energies are usually not where predicted by the double-absorber model. In some objects a log-parabola fit is better than a broken power law. By splitting the data into two equal time epochs we find that the spectral shape of many objects varies over time.