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Published October 1, 2012 | Published
Journal Article Open

Nucleosynthetic Layers in the Shocked Ejecta of Cassiopeia A

Abstract

We present a three-dimensional analysis of the supernova remnant Cassiopeia A using high-resolution spectra from the Spitzer Space Telescope. We observe supernova ejecta both immediately before and during the shock-ejecta interaction. We determine that the reverse shock of the remnant is spherical to within 7%, although the center of this sphere is offset from the geometric center of the remnant by 810 km s^(–1). We determine that the velocity width of the nucleosynthetic layers is ~1000 km s^(–1) over 4000 arcsec^2 regions, although the velocity width of a layer along any individual line of sight is <250 km s^(–1). Si and O, which come from different nucleosynthetic layers in the progenitor star, are observed to be coincident in velocity space in some directions, but segregated by up to ~500 km s^(–1) in other directions. We compare these observations of the nucleosynthetic layers to predictions from supernova explosion models in an attempt to constrain such models. Finally, we observe small-scale, corrugated velocity structures that are likely caused during the supernova explosion itself, rather than hundreds of years later by dynamical instabilities at the remnant's reverse shock.

Additional Information

© 2012 American Astronomical Society. Received 2011 August 1; accepted 2012 July 1; published 2012 September 11. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. This work was supported in part by NASA/SAO Award No. AR5-6008X and NASA/JPL through award 1265552 to the University of Minnesota. K.I. thanks Alexander Heger for valuable insight into the physics of supernova explosions.

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