XMM-Newton observations of the supernova remnant IC 443: II. evidence of stellar ejecta in the inner regions

摘要

We investigate the spatial distribution of the physical and chemicalproperties of the hot X-ray emitting plasma of the supernova remnant IC 443, inorder to get important constraints on its ionization stage, on the progenitorsupernova explosion, on the age of the remnant, and its physical associationwith a close pulsar wind nebula. The hard X-ray thermal emission (1.4-5.0 keV) of IC 443 displays acentrally-peaked morphology, its brightness peaks being associated with hot(kT>1 keV) X-ray emitting plasma. A ring-shaped structure, characterized byhigh values of equivalent widths and median photon energy, encloses the PWN.Its hard X-ray emission is spectrally characterized by a collisional ionizationequilibrium model, and strong emission lines of Mg, Si, and S, requiringoversolar metal abundances. Dynamically, the location of the ejecta ringsuggests an SNR age of ~4,000 yr. The presence of overionized plasma in the inner regions of IC 443, addressedin previous works, is much less evident in our observations.