The X-ray Expansion of the Supernova Remnant Cassiopeia A

Abstract

We present the first X-ray expansion measurement of the SNR Cas A. We compared new ROSAT to archived Einstein HRI images with a separation of 17 years. The remnant is seen to be expanding, on average, at a rate of 0.20 %/yr, which is twice as fast as the expansion of the bright radio ring and two-thirds as fast as the ensemble of optical Fast Moving Knots. This argues that we are observing different hydrodynamical structures in each band, although all of these components are located on the same patchy ring. In addition, significant variations in expansion rate as a function of azimuth around the bright X-ray ring are found. These findings are discussed in the context of two classes of models, involving either an ambient medium with a uniform or monotonically decreasing density away from the center, or a pre-existing circumstellar shell.

9 pages, 2 figures, Submitted to ApJL

References in corpus (2)

• Evidence of X-ray Synchrotron Emission from Electrons Accelerated to 40 TeV in the Supernova Remnant Cassiopeia A
• The X-ray Expansion of the Supernova Remnant Cassiopeia A

Cited by in corpus (25)

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• Cassiopeia A and its Clumpy Presupernova Wind
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• Radio Spectral Index Variations and Physical conditions in Kepler's Supernova Remnant
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• The First Measurement of Cassiopeia A's Forward Shock Expansion Rate
• The Kinematics of Kepler's Supernova Remnant as revealed by Chandra
• The First X-Ray Proper-Motion Measurements of the Forward Shock in the Northeastern Limb of SN 1006
• Accelerated Electrons in Cassiopeia A: Thermal and Electromagnetic Effects
• The X-ray Expansion of the Supernova Remnant Cassiopeia A
• Kinematics of X-ray Emitting Components in Cassiopeia A
• The Identification of Infrared Synchrotron Radiation from Cassiopeia A
• Jets as diagnostics of the circumstellar medium and the explosion energetics of supernovae: the case of Cas A
• A Comparison of X-ray and Optical Emission in Cassiopeia A
• The Extraordinarily Rapid Expansion of the X-ray Remnant of Kepler's Supernova (SN1604)
• The Relation Between the Surface Brightness and the Diameter for Galactic Supernova Remnants
• Thermal and Nonthermal Emission from the Forward Shock in Tycho's Supernova Remnant
• Tests of Galactic Cosmic Ray Source Models
• Kinematics of Supernova Remnants: Status of X-Ray Observations
• Evidence for Proportionate Partition Between the Magnetic Field and Hot Gas in Turbulent Cassiopeia A
• A Study of Radio Knots within Supernova Remnant Cassiopeia A
• The forward and reverse shock dynamics of Cassiopeia A