Although emerging from a range of progenitor stars and the product of different explosion mechanisms the light curves of the various supernova types are shaped mainly by radioactive power. Core-collapse supernovae have in addition early peaks from shock breakout with a subsequent cooling phase and massive extended stars a recombination (plateau) phase. Variations occur mostly due to differences of the progenitor stars. While there appears to be a fair understanding of the light curves of SNe II, new wrinkles are emerging for SNe Ia. The photometry of SNe Ib and SNe Ic remains unsatisfactory.

Introduction

The temporal brightness variation of supernovae (SNe) as measured by photometry contains valuable and unique information on the evolution of the progenitor star and the explosion event. Combined with optical spectroscopy broad-band light curves have been the main tools for supernova investigations in the past (e.g. Minkowski 1964, Woosley & Weaver 1986, Wheeler & Harkness 1990, Kirshner 1990). The light curves are shaped by the size and mass of the progenitor star, various processes within the explosion itself, the radioactive ashes, and, in certain cases, the local environment.

Accurate photometry is mandatory to disentangle the physics driving the emission and the colors provide information on the temperature evolution. Telltale deviations from blackbody emission arise from the effects of the rapidly expanding atmosphere. The decline rates at different epochs and for supernovae of different types are indicative of the power sources, the explosion energy, and the envelope mass.