Type Ia supernova light curves

The diversity of Type Ia supernova (SN Ia) photometry is explored using a grid of 130 one-dimensional models. It is shown that the observable properties of SNe Ia resulting from Chandrasekhar-mass explosions are chiefly determined by their final composition and some measure of mixing'' in the explosion. A grid of final compositions is explored, including essentially all combinations of Ni-56, stable iron,'' and intermediate-mass elements that result in an unbound white dwarf. Light curves (and in some cases spectra) are calculated for each model using two different approaches to the radiation transport problem. Within the resulting templates are models that provide good photometric matches to essentially the entire range of observed SNe Ia. On the whole, the grid of models spans a wide range in B-band peak magnitudes and decline rates, and does not obey a Phillips relation. In particular, models with the same mass of 56Ni show large variations in their light-curve decline rates. We identify and quantify the additional physical parameters responsible for this dispersion and consider physically motivated cuts'' of the models that agree better with the Phillips relation, discussing why nature may have preferred these solutions. For example, models that produce a constant total mass of burned material of 1.1 +/- 0.1 M-circle dot do give a crude Phillips relation, albeit with much scatter. If one further severely mixes the ejecta strongly between the center and 0.8 M-circle dot (as might be the case in a delayed-detonation scenario) reasonable agreement with the Phillips relation results, although still with considerable spread. We conclude that the supernova models that occur most frequently in nature are highly constrained by the Phillips relation and that a large part of the currently observed scatter in the relation is likely a consequence of the intrinsic diversity of these objects.