ar X iv : a st ro - p h / 06 09 45 6 v 1 1 5 Se p 20 06 Numerical Simulations of Type Ia Supernova

1.1 Introduction Recent numerical simulations of Type Ia Supernova (SN Ia) explosions [1, 2] have successfully modeled the Chandrasekhar-mass deflagration scenario (for a review see [3] or J. Niemeyer's contribution to these proceedings) in three spatial dimensions. In this SN Ia model a car-bon/oxygen white dwarf (WD) star accretes matter from a binary companion until it reaches the Chandrasekhar mass. At this point, thermonuclear burning in the center of the WD forms a subsonic deflagration flame which—mediated by thermal conduction of the degenerate electrons—propagates outward. Since the resulting stratification of dense fuel and light ashes in the gravitational field is unstable (Rayleigh-Taylor instability), burning bubbles of hot ashes ascend into cold fuel. At the interfaces a secondary shear instability gives rise to the local development of turbulence which wrinkles the flame front. This effect accelerates the effective burning velocity and thus the energy generation can account for SN Ia explosions. In the explosion process the WD material is converted to iron group elements and a smaller fraction of intermediate-mass elements (like Si, S, and Ca). However, it is only the radioactive decay of 56 Ni that powers the observed lightcurve. Numerical implementations of such models must fulfill a number of requirements. They have to be robust against variations of the initial conditions in an astrophysically reasonable range, but on the other hand they are expected to explain the observed diversity of SNe Ia. The final goal is, of course, to explain the correlation between the peak luminosity and the light curve shape on the basis of theoretical models. This relation is of great importance to calibrate cosmological distance measurements. Three-dimensional SN Ia explosion simulations have reached a quality where these issues can be addressed. Furthermore, nu-cleosynthetic post-processing of the explosion data has opened the possibility to calculate synthetic light curves and spectra which can be directly compared to observations. This provides a way to discriminate between different astrophysical models (e.g. pure deflagration or delayed detonation). We present the first systematic study on what answers three-dimensional deflagration models can give. What are the possible parameters that have the potential to explain the SN Ia diversity? Among others the progenitor's carbon-to-oxygen ratio, its metallicity, and the central density at ignition are commonly suggested. In our survey we vary these three parameters independently to explore the effects on the explosion models. However, we are aware of the fact that in principle they are …