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Session 74 - Supernova Remnants.
Display session, Thursday, June 13
Great Hall,
We investigate the dynamics of young supernova remnants (SNRs) in a non-uniform external density such as might be present at the edge of a molecular cloud. Using a cylindrical, two dimensional, TVD, hydrodynamic code we perform high resolution (1024 by 2048) simulations of explosions in a smooth density transition. We improve upon previous calculations by including the inertia and kinetic energy of the stellar ejecta. The evolution is followed until the outer blast wave has swept up roughly 20 times the initial ejected mass (14.5 M_\sun). The presence of the density transition has important dynamical effects on the remnant during the pre-Sedov-Taylor evolution. When the remnant is smaller than the width of the density transition, the apparent SNR center shifts while maintaining a nearly circular shape, making the morphology at this stage difficult to distinguish from a SNR expanding in a uniform medium. Once the remnant size exceeds the transition width, it expands as two lobes with radii that approach the self-similar Sedov-Taylor solution appropriate for the gas density local to each lobe. The non-uniform density also creates a pressure imbalance in the SNR interior which drives asymmetric, non-radial flows. At early stages, the nonspherical motions should serve as a better indicator of a non-uniform external density than the morphology. This work was supported by the NSFthrough grant AST-9318959 and by the University of Minnesota Supercomputer Institute.
