Modeling the Multi-Wavelength Emission of Shell-Type Supernova Remnant RX J1713.7-3946

Emission mechanisms of the shell-type supernova remnant (SNR) RX J1713.7-3946 are studied with multi-wavelength observational data from radio, X-ray, GeV $\gamma$-ray to TeV $\gamma$-ray band. A Markov Chain Monte Carlo method is employed to explore the high-dimensional model parameter space systematically. Three scenarios for the $\gamma$-ray emission are investigated: the leptonic, the hadronic and a hybrid one. Thermal emission from the background plasma is also included to constrain the gas density, assuming ionization equilibrium, and a 2$\sigma$ upper limit of about 0.03 cm$^{-3}$ is obtained as far as thermal energies account for a significant fraction of the dissipated kinetic energy of the SNR shock. Although systematic errors dominate the $\chi^2$ of the spectral fit of all models, we find that 1) the leptonic model has the best constrained model parameters, whose values can be easily accommodated with a typical supernova, but gives relatively poor fit to the TeV $\gamma$-ray data; 2) The hybrid scenario has one more parameter than the leptonic one and improves the overall spectral fit significantly; 3) The hadronic one, which has three more parameters than the leptonic model, gives the best fit to the overall spectrum with relatively not-well-constrained model parameters and very hard spectra of accelerated particles. The uncertainties of the model parameters decrease significantly if the spectral indices of accelerated electrons and protons are the same. The hybrid and hadronic models also require an energy input into high-energy protons, which seems to be too high compared with typical values of a supernova explosion. Further investigations are required to reconcile these observations with SNR theories.