The nuclear diversity of Type Ia supernova explosions

While Type Ia supernovae (SNe Ia) have been successfully used as cosmological distance candles, there is a large diversity of explosion properties that is presently not understood, nor how this diversity is linked to the properties of their progenitors. Here we review the present status of our understanding of SN Ia progenitors, the main classes of progenitor models and recent observational constraints, the origin of the lightcurve peak - lightcurve width relation (the 'Phillips relation') and its metallicity dependence, and illustrate how different evolutionary histories produce a diversity of pre-supernova properties. We particularly emphasize the importance of the final carbon simmering phase preceding the final runaway and the role of the convective Urca process which will alter the immediate pre-supernova conditions in the exploding white dwarf. (C) 2008 Elsevier B.V. All rights reserved.