The status for the identification of specific astronomical objects as SNIa progenitors is reviewed. Single or double degenerate progenitors? Chandrasekhar or sub-Chandrasekhar mass exploders? These are the two main questions still to be answered concerning the progenitors of Type Ia supernovae. Although all four combinations may be represented in nature, searches for double degenerates seem to indicate that such systems provide a minor channel for the production of SNIa's. The more promising candidates appear to be symbiotic stars, consisting of a single degenerate star and a sub-Chandrasekhar mass star.

Introduction

The nature of the progenitors of Type Ia SNe remains highly conjectural. The fact that SNIa's occur in elliptical galaxies – where star formation ceased a very long time ago – indicates that at least in some cases there is a long delay between the formation of the progenitor and the explosion. Attention has generally concentrated on white dwarfs (WD) in binary systems, in which the explosion of the WD is triggered by accretion from the companion. Various WD explosion mechanisms are discussed by Ken'ichi Nomoto and Eli Livne at this meeting, and I will here deal with the identification of specific astronomical objects as suitable precursor candidates.