Investigating the Effects of Progenitor Metallicity on Observable Features of Chandrasekhar Mass Type Ia Supernovae and Improving Detonation Models of Sub-Chandrasekhar Mass Type Ia Supernovae

摘要

Type Ia Supernovae are generally considered to be the result of the thermonuclear disruption of carbon oxygen white dwarfs. However, the exact mechanism behind the explosion remains uncertain. The pre-explosion progenitor of a white dwarf has never been observed, so all conclusions must be drawn from comparisons between observed events and computational models. Here, work is presented on identifying spectral features indicative of progenitor metallicity. Metallicity affects the production of alpha-chain elements, which leaves imprints in the spectra. Two features are found that may be signals of progenitor metallicity, a Ti feature at 4200 A and an Fe feature at 5500 A. The second portion of this work focuses on the accurate modeling of detonations in sub-Chandrasekhar mass type Ia supernovae. The scales of the burning processes involved, compared to the size of the white dwarf, make fully resolving the detonation computationally impossible in full-star simulations. To mitigate this problem, past studies have used sub-grid scale models that attempt to capture the energetics of the explosion and post-process the results to calculate their models' nucleosynthetic products. If sub-grid models are to be believed, they must have accurate treatments of detonation physics such as curvature and shock strengthening. In low-density regions of the white dwarf, the curvature of the detonation front slows its propagation, affecting the production of intermediate mass elements. We find that the sharp density gradient in the outer radii of the white dwarf counteracts the weakening effect of curvature, resulting in more complete burning than expected in this low density region.