Galactic Positrons From Localized Sources

Abstract

The anomalous bump in the cosmic ray positron to electron ratio at $10 GeV$ can be explained as being a component from a point source that was originally harder than the primary electron background and degrades due to synchrotron and inverse Compton losses in the Galaxy while propagating to the Earth's vicinity. The fit is better than can be obtained with homogeneous injection and is attributed to a minimum age threshold. Annihilating neutralinos can provide a fair fit to the data if they have a mass just above 1/2 the mass of the $Z^o$ and if they annihilate primarily in distant density concentrations in the Galaxy. A possible observational consequence of this scenario would be intense inverse Comptonization of starlight at the Galactic center, with a sharp energy cutoff in the emergent photons as a possible signature of the neutralino mass.