Selection

The quality of the data is rather unequal, some supernovæ had follow-up very significant: until a hundred points of photometry, others were only very little suivis(moins of 5 points).

We restricted our analysis of the lightcurves to the phases where the concept of factor of stretching is relevant, i.e. , at the points of photometry ranging between -15 and +35 days compared to the maximum of luminosity. Lastly, we want to abstract ourselves from the effects which had with the own movements of the galaxies ( $0.001$).

We thus used the supernovæ which follow the following criteria:

1. More than 5 points of photometry in the band B during the time (-15, +35) days around the maximum of luminosity.
2. A first observation at the latest 5 days after the maximum.
3. A redshift higher than 0.01.

After this selection, we have a batch of 46 supernovæ observed in the filters B and V. Among these supernovæ, 15 gained from a follow-up in the filter U.