SALT : a spectral adaptive light curve template for type Ia supernovae

We present a new method to parameterize type Ia Supernovae (SN Ia) multi-color light curves. The method was developed in order to analyze the large number of SN Ia multi-color light curves measured in current high-redshift projects. The technique is based on empirically modeling SN Ia luminosity variations as a function of phase, wavelength, a shape parameter, and a color parameter. The model is trained with a sample of well-measured nearby SN Ia and then tested with an independent set of supernovae by building an optimal luminosity distance estimator that combines the supernova rest-frame luminosity, shape parameter, and color reconstructed with the model. The distances we measure using B - and V -band data show a dispersion around the Hubble line comparable or lower than obtained with other methods. With this model, we are able to measure distances using U - and B -band data with a dispersion of $0.16\pm0.05$ around the Hubble line.