Gamma-Rays from Accretion Processes and Relativistic Beams

Abstract

In this paper we review our recent works in studying the production of γ-rays from collapsed objects. The main discussed process is always the π°-decay. We simply changed the geometry of the sources, starting from the spherical symmetry to a strong anisotropy like in the beamed sources. Firstly we starded the calculations for the processes producing γ-rays via π°-decay in the spherical accretion of matter onto collapsed objects and then we moved in studying the interactions of a monoenergetic, one dimensional beam, with a Lorentz factor γ and velocity of the beam β, with the surroimding matter and radiation.

In the spherical accretion onto massive objects, the matter may be heated up to temperature as high as 10**12 K. In such a relativistic plasma, inelastic collision of protons may produce π°which are the γ-ray source. We determined the γ- ray energy production spectra in the como-ving plasma system for different temperature and expected γ- ray energy spectra for the case of spherically symmetric accretion of matter onto a black hole. The predictions of the model gauged to the quasar 3C 273 are presented. The photon-photon interaction has been taken into account. From the best fit, a dimension of the X-ray source of few times 10**17 cm is derived.

The photon energy spectra from the electron-proton (e-p) beam interactions with the matter and radiation were calculated. We obtained the photon energy spectra from Inverse Compton Scattering (ICS) of an arbitrary background radiation by relativistic electron-beams and photon energy spectra from p + p interactions via π°-decay for relativistic proton-beams. The results for selected beam Lorentz factors and selected angles between the emitted photon direction and the beam axis are presented. The calculated theoretical spectra from ICS of the background photons by relativistic electrons and from the interaction of beamed relativistic particles with the surrounding matter have been succesfully used to fit the spectrum of Cyg X-1, in the energy range greater than 1 MeV, and that of Geminga in the COS B energy range, respectively.