X-ray Studies of the Inverted Ejecta Layers in the Southeast Area of Cassiopeia A

Abstract

The central strong activities in core-collapse supernovae expect to produce the overturning of the Fe- and Si/O-rich ejecta during the supernova explosion based on multi-dimensional simulations. X-ray observations of the supernova remnant Cassiopeia A have indicated that the Fe-rich ejecta lies outside the Si-rich materials in the southeastern region, which is consistent with the hypothesis on the inversion of the ejecta. We investigate the kinematic and nucleosynthetic properties of the inverted ejecta layers in detail to understand its formation process using the data taken by the Chandra X-ray Observatory. Three-dimensional velocities of Fe- and Si/O-rich ejecta are obtained as $>$4,500 km s${}^{-1}$ and $\sim$2,000--3,000 km s${}^{-1}$, respectively, by combining proper motion and line-of-sight velocities, indicating that the velocity of the Si/O-rich ejecta is slower than that of the Fe-rich ejecta since the early stage of the explosion. To constrain their burning regime, the Cr/Fe mass ratios are evaluated as $0.51_{-0.10}^{+0.11}$% in the outermost Fe-rich region and $1.24_{-0.20}^{+0.19}$% in the inner Fe/Si-rich region, suggesting that the complete Si burning layer is invertedly located to the incomplete Si burning layer. All the results support the ejecta overturning at the early stages of the remnant's evolution or during the supernova explosion of Cassiopeia A.

ApJ accepted. 11 pages, 7 figures

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Cited by in corpus (4)

• Richardson-Lucy deconvolution with a spatially Variant point-spread function of Chandra: Supernova Remnant Cassiopeia A as an Example
• Kinematics of Supernova Remnants Using Multiepoch Maximum Likelihood Estimation: Chandra Observation of Cassiopeia A as an Example
• Near-Infrared Spectroscopy of Dense Ejecta Knots in the Outer Eastern Area of the Cassiopeia A Supernova Remnant
• XRISM Observations of Cassiopeia A: Overview, Atomic Data, and Spectral Models