A Decade-Baseline Study of the Plasma States of Ejecta Knots in Cassiopeia A. (arXiv:1305.1581v1 [astro-ph.HE])

A Decade-Baseline Study of the Plasma States of Ejecta Knots in Cassiopeia A. (arXiv:1305.1581v1 [astro-ph.HE]):
We present the analysis of 21 bright X-ray knots in the Cassiopeia A
supernova remnant from observations spanning 10 yr. We performed a
comprehensive set of measurements to reveal the kinematic and thermal state of
the plasma in each knot, using a combined analysis of two high energy
resolution High Energy Transmission Grating (HETG) and four medium energy
resolution Advanced CCD Imaging Spectrometer (ACIS) sets of spectra. The ACIS
electron temperature estimates agree with the HETG-derived values for
approximately half of the knots studied, yielding one of the first comparisons
between high resolution temperature estimates and ACIS-derived temperatures. We
did not observe the expected spectral evolutionpredicted from the ionization
age and density estimates for each knotin all but three of the knots studied.
The incompatibility of these measurements with our assumptions has led us to
propose a dissociated ejecta model, with the metals unmixed inside the knots,
which could place strong constraints on supernova mixing models.