On the break in the fermi-large area telescope spectrum of 3C 454.3

Abstract

Fermi Gamma-ray Space Telescope observations of the flat spectrum radio quasar 3C 454.3 show a spectral-index change ΔΓ ≅ 1.2 ± 0.3 at break energy E br 2.4 ± 0.3 GeV. Such a sharp break is inconsistent with a cooling electron distribution and is poorly fit with a synchrotron self-Compton model. We show that a combination of two components, namely, the Compton-scattered disk and broad-line region (BLR) radiations, explains this spectral break and gives a good fit to the quasi-simultaneous radio, optical/UV, X-ray, and γ-ray spectral energy distribution observed in 2008 August. A sharp break can be produced independent of the emitting region's distance from the central black hole if the BLR has a gradient in density αR -2, consistent with a wind model for the BLR. © 2010. The American Astronomical Society. All rights reserved.