On the Light Curve of Type I Supernovae

Abstract

Many authors have spoken about an ‘average light curve’ for type I supernovae, giving also parameters to define it, but no one has shown so far how this curve can be built up using the data available in the literature. With this average curve at hand, one has the possibility to see whether SN I form a homogeneous class and find their general properties from the photometric point of view, above all the intrinsic dispersion at maximum which is of prime importance if these objects are to be used as distance indicators. To this aim we collected the blue light curves of 38 supernovae classified as type I, with sufficient photometric observations. Then, by shifting the individual curves in both coordinates and aiming to the least dispersion, we got the result shown in Figure 1. Here the shift on the time axis has been obviously limited to the uncertainty on the epoch of maximum as reported in the sources. The scatter seen in the figure should be largely due to the intrinsic dispersion of the ‘shape’ of type I light curves. Of course, especially in the linear decline, also errors coming from the photometry are present.