Evaluating Systematic Dependencies of Type Ia Supernovae: The Influence of Deflagration to Detonation Density
Abstract
We explore the effects of the deflagration to detonation transition (DDT) density on the production of ^{56}Ni in thermonuclear supernova (SN) explosions (Type Ia supernovae). Within the DDT paradigm, the transition density sets the amount of expansion during the deflagration phase of the explosion and therefore the amount of nuclear statistical equilibrium (NSE) material produced. We employ a theoretical framework for a wellcontrolled statistical study of twodimensional simulations of thermonuclear SNe with randomized initial conditions that can, with a particular choice of transition density, produce a similar average and range of ^{56}Ni masses to those inferred from observations. Within this framework, we utilize a more realistic "simmered" white dwarf progenitor model with a flame model and energetics scheme to calculate the amount of ^{56}Ni and NSE material synthesized for a suite of simulated explosions in which the transition density is varied in the range (13) ×10^{7} g cm^{3}. We find a quadratic dependence of the NSE yield on the log of the transition density, which is determined by the competition between plume rise and stellar expansion. By considering the effect of metallicity on the transition density, we find the NSE yield decreases by 0.055 ± 0.004 M _{sun} for a 1 Z _{sun} increase in metallicity evaluated about solar metallicity. For the same change in metallicity, this result translates to a 0.067 ± 0.004 M _{sun} decrease in the ^{56}Ni yield, slightly stronger than that due to the variation in electron fraction from the initial composition. Observations testing the dependence of the yield on metallicity remain somewhat ambiguous, but the dependence we find is comparable to that inferred from some studies.
 Publication:

The Astrophysical Journal
 Pub Date:
 September 2010
 DOI:
 10.1088/0004637X/720/1/99
 arXiv:
 arXiv:1007.1138
 Bibcode:
 2010ApJ...720...99J
 Keywords:

 hydrodynamics;
 nuclear reactions;
 nucleosynthesis;
 abundances;
 supernovae: general;
 white dwarfs;
 Astrophysics  Solar and Stellar Astrophysics;
 Astrophysics  Cosmology and Extragalactic Astrophysics;
 Astrophysics  High Energy Astrophysical Phenomena
 EPrint:
 15 pages, 13 figures, accepted to ApJ on July 6, 2010