SIMBAD references

We examine the second EGRET catalog to assess whether some unidentified >100MeV γ-ray sources are associated with supernova remnants (SNRs). We find that the 95% confidence error contours of 5 high confidence and 2 marginal unidentified γ-ray sources are coincident with SNRs. The most interesting associations are with SNRs that appear to be interacting with molecular clouds, namely IC 443, γ Cygni, and W28. We consider whether the γ-ray emission originates from pulsars, cosmic-ray interactions or, on the basis of time variability, compact objects. We compare the γ-ray spectrum of the source 2EG J0618+2234 associated with IC 443 with the results of a cosmic ray interaction γ-ray production model. A power-law proton spectrum with index -2.2 plus a very soft power-law primary accelerated electron spectrum with index ~-3.5 can reproduce the observed γ-ray spectrum.