Evaluating Systematic Dependencies of Type Ia Supernovae: The Influence of Deflagration to Detonation Density

We explore the effects of the deflagration to detonation transition density on the production of ⁵⁶Ni in thermonuclear supernova explosions (type Ia supernovae). The transition density indirectly sets the amount of expansion during the deflagration phase of the explosion and therefore the amount of Fe-group material produced. A fraction of the Fe-group material will be radioactive ⁵⁶Ni that powers the supernova lightcurve. We employ a theoretical framework for a well-controlled statistical study of two-dimensional simulations of thermonuclear supernovae with randomized initial conditions that produce ⁵⁶Ni masses with a similar average and range to those inferred from observations (Townsley et al. 2009) for a fiducial transition density of 10⁷ g cm^-3. Within this framework, we utilize a realistic 'simmered' white dwarf progenitor model and a detailed flame model and energetics scheme to calculate the amount of Fe-group material synthesized for a suite of simulated explosions in which the transition density is varied. Understanding the effect of transition density on the amount of Fe-group material produced in combination with the effect of ²²Ne (and metallicity) on transition density allows us to construct the functional dependence of the amount of Fe-group material and ⁵⁶Ni mass synthesized in the explosion on metallicity through the ²²Ne content.

This work was supported by NASA under grant No. NNX09AD19G and utilized resources at the New York Center for Computational Sciences at Stony Brook University/Brookhaven National Laboratory, which is supported by the U.S. Department of Energy under Contract No. DE-AC02-98CH10886 and by the State of New York.