Soma De, F. X. Timmes, Themis Athanassiadou, David A. Chamulak, Wendy Hawley, Dennis Jack, Edward F. Brown, Alan C. Calder, Dean M. Townsley
We present evidence that the electron fraction of the progenitor white dwarf systematically influences the nucleosynthesis of silicon group ejecta in supernova type Ia explosions. In particular, we demonstrate that the abundances generated when quasi nuclear statistical equilibrium conditions apply are preserved during the subsequent freezeout. Analytical relations and post-processing of 1D models show \silicon[28] is insensitive to the electron fraction, \sulfur[32] has a nearly linear trend with the electron fraction, and \calcium[40] has a nearly quadratic trend with electron fraction. We verify that these trends in the nucleosynthesis are reflected in synthetic spectra. We then explore a new method, based on the quasi nuclear statistical equilibrium equations, which suggests that measurement of $\ysi$, $\ys/\ysi$, $\yca/\ys$, and $\yfe/\ysi$ in an observed \SNeIa\ spectra can be used to constrain the electron fraction in silicon-rich regions. Measuring these four quantities from the the synthetic spectra generated by our explosion models is sufficient to recover our input $\ye$ to within 6%. Thus, we offer a method to determine the electron fraction of the progenitor from observations.
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http://arxiv.org/abs/1304.4942
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