Extracting x rays, gamma rays, and relativistic e-e+ pairs from supermassive Kerr black holes using the Penrose mechanism.

Abstract

Monte Carlo computer simulations of Compton scattering and ${\mathit{e}}^{\mathrm{\ensuremath{-}}}$${\mathit{e}}^{+}$ pair production processes, in the ergosphere of a supermassive (\ensuremath{\sim}${10}^{8}$${\mathit{M}}_{\mathrm{\ensuremath{\bigodot}}}$) rotating black hole, are presented. Particles from an accretion disk surrounding the black hole fall into the ergosphere and scatter off particles that are in bound orbits. In this paper, the equations that govern the orbital trajectory of a particle about a Kerr black hole (KBH) are used to derive analytical expressions for the conserved energy and angular momentum of material and massless particles that have orbits not confined to the equatorial plane. The escape conditions to determine whether or not a particle escapes from the potential well of the KBH are applied to the scattered particles. The Penrose mechanism, in general, allows rotational energy of a KBH to be extracted by scattered particles escaping from the ergosphere to large distances from the black hole. The results of these model calculations, presented in this paper, show that the Penrose mechanism is capable of producing the astronomically observed high energy particles (\ensuremath{\sim} GeV) emitted by quasars and other active galactic nuclei (AGN). This mechanism can extract hard x-ray and \ensuremath{\gamma}-ray photons, from Penrose Compton scatterings of initially low energy UV and soft x-ray photons by target orbiting electrons in the ergosphere; such low energy infalling photons, and high energy scattered escaping photons, are consistent with observations and popular theoretical accretion disk, black hole models. The Penrose pair production processes (\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{\ensuremath{-}}}$), presented here, allow relativistic ${\mathit{e}}^{\mathrm{\ensuremath{-}}}$${\mathit{e}}^{+}$ pairs to escape with energies up to \ensuremath{\sim}2 GeV; these pairs are produced when infalling low energy photons collide with bound target, highly blueshifted photons at the photon orbit. This process may very well be the origin of the relativistic electrons inferred, from observations, to emerge from the cores of AGN. Overall, these Penrose processes can apply to any mass size black hole, more or less, and suggest a complete theory for the extraction of energy from a black hole.