THE BEAMING PATTERN OF EXTERNAL COMPTON EMISSION FROM RELATIVISTIC OUTFLOWS: THE CASE OF ANISOTROPIC DISTRIBUTION OF ELECTRONS

The beaming pattern of radiation emitted by a relativistically moving source, such as jets in microquasars, active galactic nuclei, and gamma-ray bursts, is a key issue for understanding acceleration and radiation processes in these objects. In this paper, we introduce a formalism based on a solution of the photon transfer equation to study the beaming patterns for emission produced by electrons accelerated in the jet and the upscattering photons of low-energy radiation fields of external origin (the so-called external Compton scenario). The formalism allows us to treat non-stationary, non-homogeneous, and anisotropic distributions of electrons, but assuming homogeneous/isotropic and non-variable target photon fields. We demonstrate the non-negligible impact of the anisotropy in the electron distribution on angular and spectral characteristics of the EC radiation.