Sj. Sturner et al., ARE SUPERNOVA-REMNANTS SOURCES OF GREATER-THAN-100 MEV GAMMA-RAYS, Astronomy & Astrophysics. Supplement series, 120(4), 1996, pp. 445-448
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.