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

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 n {sub H} ∼ 0.9 ± 0.3 cm{sup –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 M {sub ☉}, and its mass before themore » explosion was about 5 M {sub ☉}, with uncertainties of several tens of percent. Furthermore, the results suggest that, among the mass lost from the progenitor star (∼11 M {sub ☉}), a significant amount (more than 6 M {sub ☉}) could have been via its RSG wind.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4]
  1. Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of)
  2. Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States)
  3. Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854-8019 (United States)
  4. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
Publication Date:
OSTI Identifier:
22356533
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 789; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMPARATIVE EVALUATIONS; EMISSION; EXPLOSIONS; MASS TRANSFER; MATHEMATICAL SOLUTIONS; SPECTROSCOPY; STARS; STELLAR WINDS; SUPERNOVA REMNANTS; VISIBLE RADIATION; X RADIATION