Where was the Iron Synthesized in Cassiopeia A?

Abstract

We investigate the properties of Fe-rich knots on the east limb of the Cassiopeia A supernova remnant using observations with Chandra/ACIS and analysis methods developed in a companion paper. We use the fitted ionization age and electron temperature of the knots to constrain the ejecta density profile and the Lagrangian mass coordinates of the knots. Fe-rich knots which also have strong emission from Si, S, Ar, and Ca are clustered around mass coordinates q~0.35-0.4 in the shocked ejecta; for ejecta mass 2M_sun, this places the knots 0.7-0.8 M_sun out from the center (or 2-2.1 M_sun, allowing for a 1.3 M_sun compact object). We also find an Fe clump that is evidently devoid of line emission from lower mass elements, as would be expected if it were the product of alpha-rich freeze out; the mass coordinate of this clump is similar to those of the other Fe knots.

submitted to ApJ, companion to Laming & Hwang; 25 pages, 6 figures

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• On the Determination of Ejecta Structure and Explosion Asymmetry from the X-ray Knots of Cassiopeia A
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• Ionization Equilibrium Timescales in Collisional Plasmas
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• A Detailed Kinematic Map of Cassiopeia A's Optical Main Shell and Outer High-Velocity Ejecta
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• Modeling SNR Cassiopeia A from the Supernova Explosion to its Current Age: The role of post-explosion anisotropies of ejecta
• The Bubble-like Interior of the Core-Collapse Supernova Remnant Cassiopeia A
• The fully developed remnant of a neutrino-driven supernova: Evolution of ejecta structure and asymmetries in SNR Cassiopeia A
• Population study of Galactic supernova remnants at very high $\gamma$-ray energies with H.E.S.S.
• Discovery of Outlying, High-Velocity Oxygen-Rich Ejecta in Cassiopeia A
• The Three-Dimensional Structure of Interior Ejecta in Cassiopeia A at High Spectral Resolution
• An HST Survey of the Highest-Velocity Ejecta in Cassiopeia A
• Ejecta Knot Flickering, Mass Ablation, and Fragmentation in Cassiopeia A
• Evidence for past interaction with an asymmetric circumstellar shell in the young SNR Cassiopeia A
• Near-Infrared and Optical Limits for the Central X-ray Point Source in the Cassiopeia A Supernova Remnant
• X- and Gamma-ray Studies of Cas A: Exposing Core Collapse to the Core
• Suzaku X-Ray Imaging and Spectroscopy of Cassiopeia A
• Kinematics of X-ray Emitting Components in Cassiopeia A
• A Decline in the Nonthermal X-ray Emission from Cassiopeia A
• Nonthermal radiation of young supernova remnants: the case of Cas A
• Can Ejecta-Dominated Supernova Remnants be Typed from their X-ray Spectra? The Case of G337.2-0.7
• Discovery of Fast-Moving X-Ray--Emitting Ejecta Knots in the Oxygen-Rich Supernova Remnant Puppis A
• High-entropy ejecta plumes in Cassiopeia A from neutrino-driven convection
• Fermi-LAT Detection of a Break in the Gamma-Ray Spectrum of the Supernova Remnant Cassiopeia A
• A Deep Chandra Observation of the Oxygen-Rich Supernova Remnant 0540-69.3 in the Large Magellanic Cloud
• The Circumstellar Medium of Cassiopeia A Inferred from the Outer Ejecta Knot Properties
• Nucleosynthetic Layers in the Shocked Ejecta of Cassiopeia A
• X-Ray Studies of Supernova Remnants: A Different View of Supernova Explosions
• Gamma-ray Observations of Explosive Nucleosynthesis Products
• Dense Iron Ejecta and Core-collapse Supernova Explosion in the Young Supernova Remnant G11.2-0.3
• Supernova progenitor stars in the initial range of 23 to 33 solar masses and their relation with the SNR Cas A
• Asymmetries of Heavy Elements in the Young Supernova Remnant Cassiopeia A
• A Decade-Baseline Study of the Plasma States of Ejecta Knots in Cassiopeia A
• Radioactivity and Electron Acceleration in Supernova Remnants
• Constraints on the kinematics of the 44Ti ejecta of Cassiopeia A from INTEGRAL/SPI
• A Review of X-ray Observations of Supernova Remnants
• X-ray Studies of the Inverted Ejecta Layers in the Southeast Area of Cassiopeia A
• Six Years of Chandra Observations of Supernova Remnants
• Narrow Band Chandra X-ray Analysis of Supernova Remnant 3C391