Observational Evidence for High Neutronization in Supernova Remnants: Implications for Type Ia Supernova Progenitors
- Department of Physics and Astronomy and Pittsburgh Particle Physics, Astrophysics and Cosmology Center (PITT PACC), University of Pittsburgh, 3941 O’Hara Street, Pittsburgh, PA 15260 (United States)
- NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771 (United States)
- E.T.S. Arquitectura del Vallès, Universitat Politècnica de Catalunya, Carrer Pere Serra 1-15, E-08173 Sant Cugat del Vallès (Spain)
- The Joint Institute for Nuclear Astrophysics (United States)
- Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL (United States)
- Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
- CRESST and X-ray Astrophysics Laboratory, NASA Goddard Space Flight Center, Code 602, Greenbelt, MD 20771 (United States)
- Department of Physics, University of Texas at Arlington, Box 19059, Arlington, TX 76019 (United States)
The physical process whereby a carbon–oxygen white dwarf explodes as a Type Ia supernova (SN Ia) remains highly uncertain. The degree of neutronization in SN Ia ejecta holds clues to this process because it depends on the mass and the metallicity of the stellar progenitor, and on the thermodynamic history prior to the explosion. We report on a new method to determine ejecta neutronization using Ca and S lines in the X-ray spectra of Type Ia supernova remnants (SNRs). Applying this method to Suzaku data of Tycho, Kepler , 3C 397, and G337.2−0.7 in the Milky Way, and N103B in the Large Magellanic Cloud, we find that the neutronization of the ejecta in N103B is comparable to that of Tycho and Kepler , which suggests that progenitor metallicity is not the only source of neutronization in SNe Ia. We then use a grid of SN Ia explosion models to infer the metallicities of the stellar progenitors of our SNRs. The implied metallicities of 3C 397, G337.2−0.7, and N103B are major outliers compared to the local stellar metallicity distribution functions, indicating that progenitor metallicity can be ruled out as the origin of neutronization for these SNRs. Although the relationship between ejecta neutronization and equivalent progenitor metallicity is subject to uncertainties stemming from the {sup 12}C + {sup 16}O reaction rate, which affects the Ca/S mass ratio, our main results are not sensitive to these details.
- OSTI ID:
- 22663449
- Journal Information:
- Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 843; ISSN ASJOAB; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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