The beaming of external Compton emission

TL;DR

This paper calculates the beaming pattern of external Compton emission from a relativistically moving electron blob, using full Klein-Nishina cross section and exact incident photon distribution, improving upon previous models.

Contribution

It provides a more accurate computation of the Compton scattering beaming pattern by incorporating the full Klein-Nishina cross section and exact incident photon distribution.

Findings

The approach yields a different absolute number of scattered photons compared to previous models.

The calculated boost factor is slightly lower and varies with the spectral index p.

Results show good agreement in the Thomson regime but differ in absolute photon counts.

Abstract

We consider a relativistically moving blob consisting of an isotropic electron distribution that Compton-scatters photons from an external isotropic radiation field. We compute the resulting beaming pattern, i.e. the distribution of the scattered photons, in the blob frame as well as in the observer's frame by using the full Klein-Nishina cross section and the exact incident photon distribution. In the Thomson regime the comparison of our approach with Dermer 1995 results in concurrent characteristics but different absolute number of the scattered photons by a factor of f_corr = 3.09. Additionally, our calculation yields a slightly lower boost factor which varies the more from the corresponding value in Dermer 1995 the higher the spectral index p of the electron distribution gets.