X-ray observation of the shocked red supergiant wind of Cassiopeia A

Abstract

Cas A is a Galactic supernova remnant whose supernova explosion is observed to be of Type IIb from spectroscopy of its light echo. Having its SN type known, observational constraints on the mass-loss history of Cas A's progenitor can provide crucial information on the final fate of massive stars. In this paper, we study X-ray characteristics of the shocked ambient gas in Cas A using the 1 Ms observation carried out with the Chandra X-Ray Observatory and try to constrain the mass-loss history of the progenitor star. We identify thermal emission from the shocked ambient gas along the outer boundary of the remnant. Comparison of measured radial variations of spectroscopic parameters of the shocked ambient gas to the self-similar solutions of Chevalier show that Cas A is expanding into a circumstellar wind rather than into a uniform medium. We estimate a wind density nH ~ 0.9 $\pm$ 0.3 cm${}^{-3}$ at the current outer radius of the remnant (~3 pc), which we interpret as a dense slow wind from a red supergiant (RSG) star. Our results suggest that the progenitor star of Cas A had an initial mass around 16 Msun, and its mass before the explosion was about 5 Msun, with uncertainties of several tens of percent. Furthermore, the results suggest that, among the mass lost from the progenitor star (~11 Msun), a significant amount (more than 6 Msun) could have been via its RSG wind.

ApJ Accepted. 11 pages (with emulateapj style)

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• A JWST Survey of the Supernova Remnant Cassiopeia A
• Evidence for past interaction with an asymmetric circumstellar shell in the young SNR Cassiopeia A
• Low-Frequency Radio Absorption in Cassiopeia A
• Progenitor Mass Distribution of Core-Collapse Supernova Remnants in Our Galaxy and Magellanic Clouds based on Elemental Abundances
• Infrared Supernova Remnants and their Infrared to X-ray Flux Ratios
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• Near-Infrared Knots and Dense Fe Ejecta in the Cassiopeia A Supernova Remnant
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• Detection of the Red Supergiant Wind from the Progenitor of Cassiopeia A
• Near-infrared Extinction due to Cool Supernova Dust in Cassiopeia A
• Detection of Pristine Circumstellar Material of the Cassiopeia A Supernova
• Multi-Year X-ray Variations of Iron-K and Continuum Emissions in the Young Supernova Remnant Cassiopeia A
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• Discovery of a shock-compressed magnetic field in the north-western rim of the young supernova remnant RX J1713.7-3946 with X-ray polarimetry
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• X-ray diagnostics of Cassiopeia A's "Green Monster": evidence for dense shocked circumstellar plasma
• A Large-field J=1-0 Survey of CO and Its Isotopologues Toward the Cassiopeia A Supernova Remnant
• He abundance of Dense Circumstellar Clumps in the Cassiopeia A Supernova Remnant
• The time-dependent Rayleigh-Taylor instability in interstellar shells and supershells, including the eROSITA bubbles
• Supernova Remnants as Clues to Their Progenitors
• An Exploration of X-ray Supernova Remnants in the Milky Way and Nearby Galaxies
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• HST Proper Motion Measurements of Supernova Remnant N132D: Center of Expansion and Age
• XRISM Observations of Cassiopeia A: Overview, Atomic Data, and Spectral Models
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• Bridging the gap between supernovae and their remnants through multi-dimensional hydrodynamic modeling
• The forward and reverse shock dynamics of Cassiopeia A