Schedule Feb 10, 2006
Large Ejecta Fragments in Evolved SNRs
Plucinsky, Gaetz, Edgar, Sasaki

Standard models of SNR evolution indicate that after the shock has swept-up an amount of mass significantly larger the SN ejecta, the ejecta should be well-mixed with the swept-up ISM and difficult to observe. Aschenbach (1995) suggested that the \"bullet-like$quot; features seen near the outer rim of the Vela SNR are large fragments of ejecta which have recently caught up to and passed through the shock. Follow-up observations on the Vela fragments A (Miyata 2001) and D (Plucinsky 2001 and Katsuda 2005) indicated significantly enhanced abundances consistent with the ejecta hypothesis. It is somewhat surprising to find such large fragments of ejecta in a SNR which is approximately 18,000 yr old. Simulations by Wang and Chevalier (2002) indicate that such fragments can only survive if they are rather massive and have a density contrast which is ~1000 times that of the ambient medium. We will review the properties of the apparent fragments in Vela and review the possible existence of such fragments in other SNRs.

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