Binary Evolution of Type Ia Supernovae

Observations of Type Ia supernovae (SN~Ia) combined with modeling of dynamics, light curves and spectra continue to point to the difficult conclusion that SN~Ia result from degenerate ignition in a carbon/oxygen white dwarf of the Chandrasekhar mass. Such a model accounts well for the normal" SN~Ia and for the observed dispersion exemplified by the light curve amplitude-shape relation. The criterion that the white dwarfs involved in this process grow to nearly 1.4 Msun continues to provide a great challenge to understanding the binary stellar evolution involved. The so-called supersoft X-ray sources" may provide an important new population of SN~Ia progenitors. Other techniques are being developed that may constrain the binary evolution.