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A. Lewin (Imperial College, London and UC, Davis)
Recent papers by two groups of observers have presented evidence for an accelerating universe using measurements of Type Ia supernovae (Riess et. al. 1998 and Perlmutter et. al. 1999). The different groups have used three different methods of analysing the light curves of the supernovae in order to put them on the Hubble diagram.
We have fit the data from Riess et. al. 1998 using the method in Perlmutter et. al. 1999 in order to directly compare the different fitting methods. We find that though the directly fit parameters from the light curve are in general consistent with each other, the final distance moduli obtained are not, mainly due to differences in the width-brightness relations used. Though the distances appear to be inconsistent, this does not change the overall conclusions of the papers mentioned above.
We also look at the goodness of fit of the templates to the data for different fitting methods. The high redshift data is generally fit reasonably well by the methods we look at. We use new nearby supernovae light curves to investigate further the quality of current light curve parametrizations.
This work has been funded by PPARC and UC Davis.