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Session 74 - Supernova Remnants.
Display session, Thursday, June 13
Using VLA maps of Cas A at 6cm over a time baseline of 11 years we have found azimuthal asymmetries in the expansion of the diffuse radio ring of this shell-type SNR. The range of these azimuthal variation is a factor of two in expansion rate, which in turn implies dynamical ages from 750 years to 1,500 years. The lowest expansion rate corresponds to the region where Cas A is interacting with a molecular cloud. The variations in dynamical age suggest that at different azimuthal angles, Cas A is in different evolutionary stages. We will compare the observed brightness changes of the diffuse ring with those expected from adiabatic expansion losses. We will also compare these results to other work on the motions of compact radio and optical features.
Program listing for Thursday