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Session 58 - Gamma Rays & Cosmic Rays.
Oral session, Tuesday, January 16
Salon del Rey South, Hilton

[58.06] EGRET Observations of Radio Bright Supernova Remnants

J. A. Esposito, P. Sreekumar (USRA NASA/GSFC), S. D. Hunter (NASA/GSFC), G. Kanbach (MPE)

Data from Phase 1 through Phase 3 of EGRET observations have been analyzed for gamma-ray emission near supernova remnants (SNRs) with radio flux greater than 1 Jy at 1 GHz. Comparision of the position of unidentified gamma ray sources from the second EGRET catalog (Thompson et al. 1995, ApJS, in press) with fourteen SNRs near the Galactic plane, |b| < 10\deg, indicates a statistically significant correlation, with a probability of chance coincidence better than 2 \times 10^-5 for five of thirty-two unidentified EGRET gamma ray sources being spatially consistant with radio bright SNRs.

Four of the unidentified EGRET sources studied have strong spatial correlations with radio bright SNRs associated with nearby medium mass (\sim 5000\rm\ M_ødot) molecular clouds. In these cases the mass of the molecular cloud is substantially greater than the mass of the SNR. If the gamma-ray emission is assumed to originate from cosmic rays accelerated in the SNR and interacting with the molecular cloud then, the inferred cosmic ray density in the vicinity of the SNRs is significantly enhanced compared to the average Galactic cosmic ray density in the Solar neighborhood (Esposito et al. 1996, ApJ, in press). This result supports the explanation of SNRs being the dominant acceleration site, and possibly the source, of Galactic cosmic rays.

Spectral analysis has been performed on two unidentified EGRET sources, 2EG J2020-4026 and 2EG J0618+2234, which are spatially correlated with \gamma\rm\, Cygni and IC443 respectively. The spectral index of both sources is consistant with a cosmic ray source spectral index \sim2. However, the spectral analysis is photon limited above 2 GeV.

The gamma-ray intensity or upper limit for all fourteen SNRs and spectra of 2EG J2020-4026 and 2EG J0618+2234 will be presented along with interpretation of the results.

Program listing for Tuesday