ARE SUPERNOVA-REMNANTS SOURCES OF GREATER-THAN-100 MEV GAMMA-RAYS

We examine the second EGRET catalog to assess whether some unidentifie d > 100 MeV gamma-ray sources are associated with supernova remnants ( SNRs). We find that the 95% confidence error contours of 5 high confid ence and 2 marginal unidentified gamma-ray sources are coincident with SNRs. The most interesting associations are with SNRs that appear to be interacting with molecular clouds, namely IC 443, gamma Cygni, and W28. We consider whether the gamma-ray emission originates from pulsar s, cosmic-ray interactions or, on the basis of time variability, compa ct objects. We compare the gamma-ray spectrum of the source 2EG J06182234 associated with IC 443 with the results of a cosmic ray interacti on gamma-ray production model. A power-law proton spectrum with index -2.2 plus a very soft power-law primary accelerated electron spectrum with index similar to -3.5 can reproduce the observed gamma-ray spectr um.