The Beaming Pattern and Spectrum of Radiation from Inverse Compton Scattering in Blazars

Abstract

By including Klein-Nishina effects, we generalize previous calculations of the beaming pattern of photons produced by inverse Compton scattering. For an isotropic distribution of soft photons upscattered by nonthermal electrons with a power-law density distribution n(γ)~γ-p, embedded in a plasma moving with relativistic bulk speed, we show that the observed radiation intensity is proportional to D3+p, where D is the Doppler boosting factor. This agrees with previous computations performed in the Thomson limit, where the observed spectral index is α=(p-1)/2 and the beaming pattern is D4+2α. Independent of D, Klein-Nishina effects limit the location of the peak energy ɛpeakmec2 of the observed spectral energy distribution such that ɛpeak