YOUNG OXYGEN-RICH SUPERNOVA-REMNANTS .2. AN OXYGEN-RICH EMISSION MECHANISM

An emission mechanism is presented for the observed oxygen-rich plasma emission in young, oxygen-rich supernova remnants (OSNRs). The mechanism involves the interaction of a fast moving ''blob'' of oxygen-rich material with the SNR medium, forming a bow-shock/cloud-shock structure. The shock emission is then determined to drive a weak R-type ionization front through the oxygen-rich material. The combined shock and ionization front emission reproduces the major features of the observed optical and UV spectrum. Dynamical constraints based on the observed motions, lifetimes, and estimated densities of the oxygen-rich knots are used to determine model parameters. The plasma composition, predominantly [Ne/O] approximate to -0.34, used is consistent with massive stellar evolution and explosive synthesis models. Significantly, the unusually high [O III] temperature-sensitive ratio is reproduced simultaneously with the low ionization, optical, [O I], and CO III lines. The UV emission is predicted, and a good comparison is made with the UV spectrum of SNR E102.2-7219 from observations of Blair et al. (1989). Specific abundance variations were not used to make detailed fits to the observations, detailed abundance determination will require further observations. This forms the second paper in a short series; in the first paper observations for three southern OSNRs were presented. Those observations are used here along with other observations from the literature.