Nonthermal Emission from a Radio-bright Shell-Type Supernova Remnant IC 443

Abstract

By assuming diffusive shock acceleration of the nonthermal particles in the shell, we model a time-dependent nonthermal particle and photon spectra for the radio-bright shell-type supernova remnant (SNR) IC 443 with radio, optical, and X-ray emission concentrated toward the rim, whereas the γ-rays detected by EGRET are located at the center of the SNR, and the very high energy (VHE) γ-rays detected by MAGIC are displaced to the south, in direct correlation with a molecular cloud (MC). In this model, the nonthermal photon emission consists of two components, one comes from the shell evolving in the interstellar medium (ISM) and the other from the shell interacting with an MC. Our results indicate that (1) the emission from radio to soft X-ray bands is dominated by synchrotron radiation in the shell evolving in the ISM and (2) the detected high-energy emission (>10 MeV) from the SNR is from the shell evolving in the MC; i.e., the high-energy photons with energies from 10 MeV to 0.1 TeV are dominated both by bremsstrahlung and by p-p interaction, and the VHE γ-rays are produced mainly via p-p interaction.