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Session 74 - Supernova Remnants.
Display session, Thursday, June 13
Great Hall,
We describe first results from an updated X-ray nonequilibrium-ionization code using as a dynamical substrate a Sedov-Taylor blast wave appropriate for a supernova remnant (SNR). The code has extensively updated atomic physics, particularly in iron L-shell transitions, and allows an arbitrary ratio \beta of postshock electron temperature T_e to ion temperature T_i, to describe possible nonthermal plasma heating processes in the shock wave. We show that at the resolution of the ASCA X-ray satellite, our calculated models are poorly fit by simple models in the XSPEC data-reduction package, such as constant-temperature nonequilibrium-ionization ``neq'' models with a single ionization timescale. Models with the same postshock electron temperature but varying ion temperatures (i.e., varying \beta with constant \beta T_i) produce quite different high-energy continua and should be distinguishable in practice, holding out the possibility of measuring the extent of plasma heating. We show that a simple multi-zone model superposing several ``neq'' models with different temperatures and with ionization timescales chosen appropriately can provide a much better fit to our full simulations, and the fitted temperatures accurately reflect the mass-weighted temperature of our full Sedov model. We plan to adapt our models for use in XSPEC, and make them available to the general astronomical community.
