THE CIRCUMSTELLAR MEDIUM OF CASSIOPEIA A INFERRED FROM THE OUTER EJECTA KNOT PROPERTIES
- NASA/GSFC Code 662, Greenbelt, MD 20771 (United States)
We investigate the effect of the circumstellar medium density profile on the X-ray emission from outer ejecta knots in the Cassiopeia A supernova remnant using the 1 Ms Chandra observation. The spectra of a number of radial series of ejecta knots at various positions around the remnant are analyzed using techniques similar to those devised in previous papers. We can obtain a reasonable match to our data for a circumstellar density profile proportional to r {sup -2} as would arise from the steady dense wind of a red supergiant, but the agreement is improved if we introduce a small (0.2-0.3 pc) central cavity around the progenitor into our models. Such a profile might arise if the progenitor emitted a fast tenuous stellar wind for a short period immediately prior to explosion. We review other lines of evidence supporting this conclusion. The spectra also indicate the widespread presence of Fe-enriched plasma that was presumably formed by complete Si burning during the explosion, possibly via alpha-rich freezeout. This component is typically associated with hotter and more highly ionized gas than the bulk of the O- and Si-rich ejecta.
- OSTI ID:
- 21371954
- Journal Information:
- Astrophysical Journal, Vol. 703, Issue 1; Other Information: DOI: 10.1088/0004-637X/703/1/883; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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