Type Ia Supernova Light Curves

The diversity of Type Ia supernova (SN Ia) photometry is explored using agrid of 130 one-dimensional models. It is shown that the observable propertiesof SNe Ia resulting from Chandrasekhar-mass explosions are chiefly determinedby their final composition and some measure of ``mixing'' in the explosion. Agrid of final compositions is explored including essentially all combinationsof 56Ni, stable ``iron'', and intermediate mass elements that result in anunbound white dwarf. Light curves (and in some cases spectra) are calculatedfor each model using two different approaches to the radiation transportproblem. Within the resulting templates are models that provide goodphotometric matches to essentially the entire range of observed SNe Ia. On thewhole, the grid of models spans a wide range in B-band peak magnitudes anddecline rates, and does not obey a Phillips relation. In particular, modelswith the same mass of 56Ni show large variations in their light curve declinerates. We identify the physical parameters responsible for this dispersion, andconsider physically motivated ``cuts'' of the models that agree better with thePhillips relation. For example, models that produce a constant total mass ofburned material of 1.1 +/- Msun do give a crude Phillips relation, albeit withmuch scatter. The scatter is further reduced if one restricts that set tomodels that make 0.1 to 0.3 Msun of stable iron and nickel isotopes, and thenmix the ejecta strongly between the center and 0.8 Msun. We conclude that thesupernovae that occur most frequently in nature are highly constrained by thePhillips relation and that a large part of the currently observed scatter inthe relation is likely a consequence of the intrinsic diversity of theseobjects.Comment: 18 pages, submitted to ApJ on 8/18/200