ON THE NATURE OF THE EGRET SOURCE AT THE GALACTIC-CENTER

The recent detection of a gamma-ray flux from the direction of the Gal actic center by EGRET on the Compton GRO raises the question of whethe r this is a point source (possibly coincident with the massive black h ole candidate Sgr A) or a diffuse emitter. Using the latest experimen tal particle physics data and theoretical models, we examine in detail the gamma-ray spectrum produced by synchrotron, inverse Compton scatt ering, and mesonic decay resulting from the interaction of relativisti c protons with hydrogen accreting onto a point-like object. Such a dis tribution of high-energy baryons may be expected to form within an acc retion shock as the inflowing gas becomes supersonic. This scenario is motivated by hydrodynamic studies of Bondi-Hoyle accretion onto Sgr A , which indicate that many of its radiative characteristics may ultim ately be associated with energy liberated as this plasma descends into the deep potential well. Earlier attempts to analyze this process con cluded that the EGRET data are inconsistent with a massive point-like object. Here we demonstrate that a more careful treatment of the physi cs of p-p scattering suggests that a black hole of similar to 10(6) M. may be contributing to this high-energy emission.