Non-Equilibrium X-Ray Emission from Young Supernova Remnants

Citation

Nugent, John Joseph, Jr. (1983) Non-Equilibrium X-Ray Emission from Young Supernova Remnants. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/mees-s868. https://resolver.caltech.edu/CaltechTHESIS:09252017-104936539

Abstract

A computer model (NIE model) has been developed to predict the the x-ray spectra from the hot (10^6-8 K), shock-heated plasmas that are found in the rem­nants of supernovae. The model accounts for the lack of collisional ionization equilibrium and for the possible lack of thermal equilibrium between the elec­trons and ions behind the shock fronts. Both of these effects are potentially important in determining the emergent x-ray spectrum of young (≲ 10⁴ years old) supernova remnants (SNR). Both a spectral component arising from the supernova ejecta and a component arising from the shocked interstellar medium (ISM) surrounding the supernova are calculated.

The NIE model has been fit to the spectral data from two young SNR's, MSH 14-63 and RCW 103. The data from MSH 14-63 were collected with the HEAO A-2 experiment and spans an energy range from 0.18 - 15 keV. Spectral resolu­tion varies over this range. For example, ΔE/E = 32% FWHM at 1.5 keV, and ΔE/E = 15% FWHM at 7 keV. Important results from applying the model are: a significant non-Coulomb, ion-electron interaction is occurring in the remnant, presumably at the shock front; the data can be fit by a model with little or no emission from any source other than the shocked ISM with an age which is con­sistent with that of MSH 14-63; anomalous abundances of heavy elements and possible discrepancies in the centroid and shape of the Fe K_α feature could be explained by inhomogenities in the ISM density or by ejecta that have come to thermal equilibrium with the shocked ISM; and under the assumptions of the model, the distance to the MSH 14-63 is inconsistent with distance measured to an OB star group that is suggested to be associated with the remnant.

The data for RCW 103 were obtained using the Solid State Spectrometer (SSS) on board the HEAO-2 spacecraft. This data set had a more limited spectral range than above (0.8 - 2.5 keV) but enhanced spectral resolution (ΔE/E ≈ 10%). In addition, the data had limited spatial resolution. The principal results from this work are: no variation can be detected in the spectrum collected from different regions of the remnant; the data cannot be used to determine whether non-Coulomb electron-ion energy exchange processes may be present behind the shock front; and assuming that non-Coulomb processes are present - a likely hypothesis given results from other young SNR's, the data are consistent with the idea that the emission is all from the shocked interstellar medium with approximately solar composition of heavy elements.

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