3C 391: A Key to the Mixed Morphology SNR Mystery

The Mixed Morphology remnants are a newly identified SNR class, with radioshells and centrally filled thermal Xray emission. Most of their attributes,except for their Xray emission can be explained by the explosion of a massive,windless star inside a molecular cloud. Xray emission arises either fromevaporation of shocked clouds or interior gas reheated by thermal conduction. Wepropose a 30ks EPIC observation of 3C 391, a prototypical MM SNR, to performplasma diagnostics and detailed spectral mapping. 3C 391.s ASCA spectrum showsevidence of a recombining, as contrasted to an ionizing, plasma, indicating thepresence of dynamically old gas. EPIC spectroscopic confirmation will resolvethe issue of the Xray emission from MM SNR.s. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]