From: VAFadeyev@lbl.gov
Date: Wed Jan 14 2004 - 01:15:56 PST
Hi Serena,
sorry for belated comments. The paper looks very
good to me. I have one concern and a few passing
remarks:
1) You have found some correlations between
the template fitting parameters (Figs. 7-9).
Did you checked the Monte-Carlo tests data
(section 2.3) for the existence of the same
features, by any chance? Or, alternatively,
did you obtain the correlation matrix of
the fitted parameters?
My concern is that I would actually *expect*
some correlations (e.g. between the stretch
and the time of the second peak), simply
because of the way the fitting procedure
is constructed. For example, if there is
a spurious upward fluctuation on the rising
slope, that should push the stretch to higher
value; then the righ-hand-side slope of the first
peak would also be higher, and the position of
the 2nd peak shifted to a later time.
This issue may or may not be important,
it depends on how correlated the fitted parameters
are. If they are fairly independent, then
the observed correlations are due to the real
SN features. If not, then you might be seeing
an artifact of your procedure.
2) Do you have a rough estimate of how much
of the time-of-the-maximum dispersion shown in
Fig. 6 are intrinsic, i.e. not due to the
measurement errors?
3) You have alluded to the systematic trends
in the lightcurve fit residuals. Well, the artifact of rising slope in the pre-1st-maximum residuals
is very obvious. It shows up in 7 out of 9 SNe
which have an adequate pre-max coverage.
Not that I have a constructive suggestion
about this.
4) Many lightcurve fits have rather large Chisq/Dof.
Did you try to account for that when obtaining
the fit parameter errors and later on the magnitude
dispersion in the Hubble diagram? There is a
"recipy" when one artificially scales the data
errors to make Chisq/Doc = 1. (I'm just not sure
if you used this or any other way of "massaging"
the data in such cases.)
Cheers,
vitaliy
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