Photoabsorption of Gamma Rays in Relativistic Jets

Abstract

A derivation of the γγ--> e^+ e^- optical depth for γrays produced in a comoving spherical emitting region is presented. Employing a simplified expression for the γγabsorption cross section, analytic expressions for the minimum Doppler factor implied by the requirement of gamma-ray transparency are derived for a broken power-law spectrum of target photons which are isotropically distributed in the comoving frame. Application to specific systems is illustrated.

arXiv comment4 pages, in the Tenth Marcel Grossman Meeting on General Relativity, Rio de Janeiro, Brazil (July 20-26, 2003)