Thursday, August 1, 2013

1307.8221 (Min Long et al.)

Three-dimensional Simulations of Pure Deflagration Models for Thermonuclear Supernovae    [PDF]

Min Long, George C. Jordan IV, Daniel R. van Rossum, Benedikt Diemer, Carlo Graziani, Richard Kessler, Bradley Meyer, Paul Rich, Don Q. Lamb
We present a systematic study of the pure deflagration model of Type Ia supernovae, using three-dimensional, high-resolution, full-star hydrodynamical simulations, nucleosynthetic yields calculated using Lagrangian tracer particles, light curves calculated using radiation transport, and evaluation the simulations through comparison of their predicted light curves with many observed SNe Ia using the SALT2 data-driven model. We explore the effect on the properties of the simulations of different initial conditions by varying the number of ignition points and the radius of the sphere in which they are confined. The number of ignition points ranges from 63 to 3500, and they are placed randomly within confining spheres with radii of 128 km, 256 km, and 384 km whose centers coincide with the center of the white dwarf. The nuclear energy released and the final products of the nuclear burning are diverse. We find that the nuclear energy released, the kinetic energy, and the distributions of the overall mass density and the densities of $^{56}$Ni, Si, and C/O in the ejecta, all depend primarily on the number of ignition points. The simulations with few ignition points release more nuclear energy, have larger kinetic energies, and produce more $^{56}$Ni than those with many ignition points. For these reasons, the simulations with few ignition points have light curves that rise more quickly, have higher peak B-band absolute magnitudes $M_B$, and decline more rapidly than those with many ignition points. We find that, as a result, the $M_B$ and the shapes of the light curves predicted by the simulations with few ignition points have properties similar to the under-luminous SNe Iax, while those with many ignition points do not. Thus the former are a more promising explanation of these events.
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