Thermonuclear supernova simulations with stochastic ignition

Abstract

We apply an ad hoc model for dynamical ignition in three-dimensional numerical simulations of thermonuclear supernovae assuming pure deflagrations. The model makes use of the statistical description of temperature fluctuations in the pre-supernova core proposed by , ApJ, 616, 1102. Randomness in time is implemented by means of a Poisson process. We are able to vary the explosion energy and nucleosynthesis depending on the free parameter of the model which controls the rapidity of the ignition process. However, beyond a certain threshold, the strength of the explosion saturates and the outcome appears to be robust with respect to the number of ignitions. In the most energetic explosions, we find about 0.75 M of iron group elements. Other than in simulations with simultaneous multi-spot ignition, the amount of unburned carbon and oxygen at radial velocities of a few 10 3 km s −1 tends to be reduced for an ever increasing number of ignition events and, accordingly, more pronounced layering results.

On the applicability of the level set method beyond the flamelet regime in thermonuclear supernova simulations

“…On the other hand, a certain resolution is mandatory for capturing the large-scale production of turbulence by Rayleigh-Taylor instabilities. From the resolution study in Schmidt et al (2006b) and the influence of doubling the resolution of thermonuclear supernova simulations with stochastic ignition discussed by Schmidt & Niemeyer (2006), we conclude that 128 3 cells per octant are sufficient for arriving at a sensible estimate of the total amount of burning products.…”

“…Furthermore, an investigation of near-infrared emission lines of three branch-normal supernovae by Marion et al (2006) implies very little carbon residuals at radial velocities less than 1.8 × 10 4 cm s −1 . Even the most advanced three-dimensional simulations of thermonuclear supernovae assuming pure deflagrations (Röpke et al 2006;Schmidt & Niemeyer 2006) fail to satisfy this constraint. In models with delayed detonations (Gamezo et al 2005), on the other hand, the supersonic propagation of burning fronts dispose of virtually all carbon except for the outermost layers.…”

“…In this article, we shall be concerned exclusively with the Chandrasekhar mass scenario. Schmidt & Niemeyer (2006) showed that the explosion energy and mass of iron group elements in thermonuclear supernova simulations with pure deflagration can be varied over about an order of magnitude if non-simultaneous point ignitions are applied. To that end, the simple MLT model of the pre-supernova core proposed by Wunsch & Woosley (2004) was adopted for the implementation of a stochastic ignition procedure.…”

“…Due to the artificially chosen termination of thermonuclear burning at mass densities below 10 7 g cm −3 , however, the prediction of the carbon and oxygen residuals in the models with stochastic ignition by Schmidt & Niemeyer (2006) was not reliable. The transition from the flamelet regime to the regime of distributed burning is expected to occur at a mass density of about 3 × 10 7 g cm −3 (Niemeyer & Woosley 1997;Niemeyer & Kerstein 1997).…”

Multi‐dimensional numerical simulations of type Ia supernova explosions

“…A model for flame propagation based on this technique was developed by Smiljanovski et al (1997) and a modified version for thermonuclear flames in SN Ia explosion was presented by Reinecke et al (1999b) (for details of the implementation see also Hillebrandt et al, 2005). This scheme was applied in the simulations by , Reinecke et al (2002c,a,b), Röpke & Hillebrandt (2004, Röpke (2005), Schmidt et al (2005c), Schmidt & Niemeyer (2006), and Röpke et al ( , 2006a.…”