Re: possible mistake in P99 lightcurve fits

From: Alexander Conley (AJConley@lbl.gov)
Date: Thu Sep 16 2004 - 13:29:53 PDT

  • Next message: Saul Perlmutter: "Re: possible mistake in P99 lightcurve fits"

    I have now verified (using SN1998as) that snminuit behaves as I
    have stated.

    For a B only fit to 98as, tbmax = -12.572 which corresponds to
    the real date 50896.03. If I do a V band fit where tbmax is forced
    to be -12.572, the date of B maximum comes out to be 50913.82.
    Furthermore, a joint B and V fit with tbmax fixed is different that
    either of the individual fits, with the date of B maximum 50912.65.

    This procedure furthermore introduces a bias between the low
    and high redshift sample. With high quality data it is possible to
    tell that the date of V maximum is 1-2 days later than the date of
    B maximum, so the V fits will be systematically wrong by this
    amount. At high redshift there are likely to not be observations that
    can pick up on this difference, so the brightest B and V points will
    probably be the same, and therefore most of the high redshift SNe
    will not be affected by this problem.

    That is, I expect that the (B-V)max colors in P99 are systematically
    offset between the low and high redshift sample.

    Alex

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