Re: U-B color alert, feedback solicitation

From: Vitaliy Fadeyev (VAFadeyev@lbl.gov)
Date: Fri Dec 17 2004 - 10:13:16 PST

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    Dear Serena,

    thanks for your reply.
    I put your email on TWiki.

    >I have a couple of questions:
    >
    >1. which is the second outlier SN you exclude from Jha's plot?
    >
    It's 97br, which has the bluest color in the sample (U-B = -0.855).

    >2. I believe now, that the first point is 1999Y, because that should have
    >the right stretch factor. I could try to implement the 6 other SNe used by
    >Jha in my analysis if someone has the data. I have seen that Alex Conley
    >uses 2001V in the CMAGIC paper.
    >
    >**Alex, do you have the data for these 6 SNe in the snminuit format?
    >
    I'm not sure about 99Y... because it was not mentioned neither in the
    table of 22 SNe,
    not in the list of the 6 additional ones.

    >For the linear versus exponential stretch-color relation, I agree they
    >both work well in the U-B vs s(U) plot (especially given the scatter of
    >the data), once the first point (s ~0.6) is excluded. It is too bad that
    >we rely on 1 point only to define the relation function. In this moment I
    >do not see any reasons why the relation should be the same in all colours,
    >so the behavior of B-V vs stretch does not help to define the one of U-B.
    >Am I missing something important?
    >
    Admittedly, this is not a very strong argument. This is basicly a
    continuity reasoning
    that, in the absense of strong anomalies, the color behaviour in the
    adjacent bands
    cannot be to dissimilar.

    Cheers,
    vitaliy

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