Association of Unidentified, Low Latitude EGRET Sources with Supernova Remnants

Abstract

We propose that some of the unidentified Galactic plane (-10 degrees < b < 10 degrees) sources listed in the first EGRET catalog (Fichtel et al. 1994) are associated with nearby supernova remnants. The probability that the association of strong EGRET sources with supernova remnants is due to chance alignment is found to be < 1/2200. Three of the most convincing associations are radio-bright, nearby shell remnants and a fourth is associated with a plerion. We examine possible gamma-ray production mechanisms and conclude that pion production and decay from high-energy protons interacting with the remnant gas could produce the gamma rays. The energetics of this process are in accord with theories of cosmic ray production through supernova shock acceleration. The identification of pion-decay features in the gamma-ray spectra of supernova remnants would support this interpretation.