The Role of Electron Captures in Chandrasekhar-Mass Models for Type Ia Supernovae

By F. Brachwitz, David J. Dean, W. Hix, K. Iwamoto, K. Langanke, G. Mart'inez-Pinedo, Ken'ichi Nomoto, M. Strayer, Friedrich-Karl Thielemann, H. Umeda. 2000

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The Chandrasekhar-mass model for Type Ia supernovae (SNe Ia) has received increasing support from recent comparisons of observations with light-curve predictions and modeling of synthetic spectra. It explains SN Ia events via thermonuclear explosions of accreting white dwarfs in binary stellar systems, being caused by central carbon ignition when the white dwarf approaches the Chandrasekhar mass. As the electron gas in white dwarfs is degenerate, characterized by high Fermi energies for the high-density regions in the center, electron capture on intermediate-mass and Fe group nuclei plays an important role in explosive burning. Electron capture affects the central electron fraction Ye, which determines the composition of the ejecta from such explosions. Up to the present, astrophysical tabulations based on shell model matrix elements were available only for light nuclei in the sd-shell. Recently, new shell model Monte Carlo and large-scale shell model diagonalization calculations have also been performed for pf-shell nuclei. These lead in general to a reduction of electron capture rates in comparison with previous, more phenomenological, approaches. Making use of these new shell model-based rates, we present the first results for the composition of Fe group nuclei produced in the central regions of SNe Ia and possible changes in the constraints on model parameters like ignition densities ρign and burning front speeds vdef.

Subfields: Astronomy and Astrophysics, Instrumentation, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/6c271a650bc84c2a52dc0375ce695fc298e14f2a

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Citations in the corpus

COSMOLOGICAL IMPLICATIONS FROM OBSERVATIONS OF TYPE IA SUPERNOVAE (2001, background): “…Arnett 1996, Woosley & Weaver 1986, Hillebrandt & Niemeyer 2000), where the core was incinerated from carbon and oxygen to nuclear statistical equilibrium (mostly iron-group elements) (Arnett 1996, Iwamoto et al. 1999, Brachwitz et al. 2000), changes in the nuclear burning physics are not likely.”
Nucleosynthesis in multi-dimensional SN Ia explosions (2004, methodology): “Despite of the fact tha differences with respect to thestandard W7 nucleosynthesis (Iwamoto et al. 1999, Brachwitz et al. 2000, Thielemann et al. 2003) are found, in particular in the56Ni mass produced, as well as in the final amount of unburned material, in general the nuclear yields are…”
NEUTRON-RICH CHROMIUM ISOTOPE ANOMALIES IN SUPERNOVA NANOPARTICLES (2010, background): “The predicted 54Cr/52Cr ratios are probably too high because the electron capture rates used by Woosley (1997) have been subsequently revised downward (Brachwitz et al. 2000) but no comprehensive study of the nucleosynthesis of neutronrich isotopes has been published with these reduced rates.”
Three-dimensional delayed-detonation models with nucleosynthesis for Type Ia supernovae (2012, background): “…(e.g. Travaglio et al. 2004; Röpke et al. 2006a) such detailed information for delayed detonation explosion models is currently only available for a few two-dimensio al (Meakin et al. 2009; Maeda et al. 2010b) or one-dimensional explosion models (e.g. Iwamoto et al. 1999; Brachwitz et al. 2000).”
Chemical enrichment in cosmological, smoothed particle hydrodynamics simulations (2009, background): “The standard to whichmost results are compared is the spherically symmetric calculation dubbed “W7” (Nomoto et al. 1984, 1997; Iwamoto et al. 1999; Brachwitz et al. 2000; Thielemann et al. 2003).”
CHARGED-PARTICLE AND NEUTRON-CAPTURE PROCESSES IN THE HIGH-ENTROPY WIND OF CORE-COLLAPSE SUPERNOVAE (2010, methodology): “…in the) expansion of the wind until charged-particle freezeout, were performed with the Basel nucleosynthesis code (see, e.g., Thielemann et al. 1996; Brachwitz et al. 2000; Fröhlich et al. 2006a; however, not including neutrino interactions) making use of the nuclear input as described there.”
Constraints on the progenitor systems of type Ia supernovae (2005, background): “If prior to explosion there is a significant amount of alpha elements within the white dwarf, one may reasonably expect the production of more stable isotopes, thus reducing the amount of56Ni synthesized (Brachwitz et al. 2000).”
Abundances of Cu and Zn in metal-poor stars: Clues for Galaxy evolution (2002, background): “A similar (or even worst) situation occurs for type Ia supernovae (see e.g. Nomoto et al. 1984; Iwamoto et al. 1999; Brachwitz et al. 2000), and the only contributions relatively well established are those from the main component of the sprocess coming from long-lived AGB stars (Gallino et al.…”
Nuclear weak-interaction processes in stars (2002, background): “The net effect of the new rates is that, for an otherwise unchanged model, it increases the central density by about a factor of 1.3 (Brachwitz et al., 2000; Woosley, 2001).”
NUCLEOSYNTHESIS IN TWO-DIMENSIONAL DELAYED DETONATION MODELS OF TYPE Ia SUPERNOVA EXPLOSIONS (2010, background): “Detailed comparisons between the new rates and those of Fuller et al. (1982, 1985) are presented by Brachwitz et al. (2000) for the spherical 1D deflagration model W7 (see also Thielemann et al. 2004).”
Neutron star mergers versus core-collapse supernovae as dominant r-process sites in the early Galaxy (2003, methodology): “Note, that if revised, i.e. reduced electron capture rates are applied (see Brachwitz et al. 2000), the yields of model CDD2 correspond to those of model WDD2, which are more accurate in terms of central conditions.”