A Decade-Baseline Study of the Plasma States of Ejecta Knots in Cassiopeia A

Abstract

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.

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Cited by in corpus (9)

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• Asymmetries of Heavy Elements in the Young Supernova Remnant Cassiopeia A
• Multi-Year X-ray Variations of Iron-K and Continuum Emissions in the Young Supernova Remnant Cassiopeia A
• A Deep Exposure in High Resolution X-Rays Reveals the Hottest Plasma in the $\zeta$Puppis Wind
• X-ray Studies of the Inverted Ejecta Layers in the Southeast Area of Cassiopeia A
• Discovery of Year-Scale Time Variability from Thermal X-ray Emission in Tycho's Supernova Remnant
• Near-Infrared Spectroscopy of Dense Ejecta Knots in the Outer Eastern Area of the Cassiopeia A Supernova Remnant
• XMM-Newton Observations of the High Temperature Plasma in the Large Magellanic Cloud Supernova Remnant N132D