On the Spectral Break in the Fermi-LAT Spectrum of 3C 454.3
  Fermi Gamma ray Space Telescope observations of the flat spectrum radio
quasar 3C~454.3 show a spectral-index change $\Delta \Gamma \cong 1.2\pm 0.3$
at break energy $E_{br} \approx 2.4\pm0.3$ 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 $\gamma$-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 $\propto R^{-2}$, consistent with a wind model for the BLR.
