High Energy Radiation from the Galactic Black Hole Sgr A*

Abstract

We suggest that the energy source of the observed TeV, GeV and 511 KeV annihilation lines from the direction of the Galactic Center is the Galactic black hole Sgr A*, which becomes active when a captured star is tidally disrupted and matter is accreted into the black hole. During the active phase relativistic protons are ejected. GeV-TeV photons result from the decay of neutral pions produced by proton-proton collisions. Positrons lost most of their energies in the central region and diffuse to 500 pc region, where they cool to several eV via ionization loss. 511 KeV lines are produced by these thermalized positrons through the decay of positronium in warm gas. It is extremely important to notice that the energy injection is not continuous because the capture event only takes place once every 105yr and the gas density in the Galactic Center is non-uniform. We compare the observed data with model predictions. © 2007 Elsevier B.V. All rights reserved.