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**Session 44 - New Light on Supernova Remnants.**

*Display session, Wednesday, June 11*

*South Main Hall, *

## [44.04] Nonequilibrium-Ionization X-ray Spectra from a Sedov-Taylor Blast Wave Model for a Supernova Remnant

*W. J. Lyerly, S. P. Reynolds, K. J. Borkowski, J. M. Blondin (NCSU)*
We describe results from an updated X-ray nonequilibrium-ionization
code using as a dynamical substrate a Sedov-Taylor blast wave
appropriate for a supernova remnant. The code has extensively updated
atomic physics, particularly in Fe L-shell transitions, and allows for
an arbitrary ratio \beta of the postshock electron temperature T_e
to the mean temperature T, to describe possible nonthermal plasma
heating processes in the shock wave. Previous results indicate that
simple models, such as constant-temperature nonequilibrium-ionization
models, do not adequately approximate these full calculations. We
present new findings concerning the ability of XSPEC to distinguish
among our calculated, Sedov-based models using the response function
of the ASCA satellite. In all cases, the ionization timescale of the
remnant is well determined. Models with high postshock electron
temperatures (T_e = 3.5 keV) can be recognized, but only the product
of the mean temperature T and \beta can be found as models with
equal \beta T are indistinguishable. However, at lower temperatures
(T_e = 0.35 keV), XSPEC can differentiate among models having equal
values of \beta T. The value of \beta can be constrained and T
is found to within 5%. Proper spectral binning is essential to these
results because of the influence of \beta on the high-energy portion
of the spectrum where photon counts are low. We also investigate the
observed flux level required to make such distinctions at ASCA
resolution and sensitivity. Due to the complexity of the Sedov-Taylor
substrate, the models cannot be generated for real-time fitting. We
have generated a substantial grid of models, which map a
three-dimensional parameter space in postshock temperature, ionization
parameter, and \beta. We plan to make these XSPEC-ready models
available to the general astronomical community.

The author(s) of this abstract have provided an email address for comments about the abstract: wjlyerly@unity.ncsu.edu

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