Identifying breaks and curvature in the Fermi spectra of bright flat spectrum radio quasars

Abstract

Knowing the site of γ-ray emission in active galactic nucleus 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 γ-rays with photons from the broad-line region could become significant. Such absorption is predicted to produce two specific spectral breaks in the γ-ray spectra of Flat Spectrum Radio Quasars (FSRQs). We test this hypothesis using three 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. © 2012. The American Astronomical Society. All rights reserved..