From: Lifan Wang (lifan@panisse.lbl.gov)
Date: Fri Mar 14 2003 - 11:15:15 PST
Would not this error floor introduce unreasonably large errors at the
late time light curves ? At day 40, the supernova is about 3 magnitude
fainter, i.e. the flux is about 0.063 times that of the peak. The error
floor then implies late time errors are around above 0.1 mag and increases
at later epoch. I don't think this is the correct way of treating the
data, as the measurement can definitely be better than the error floor.
Also, if you fit to a pure power law to many of the nebular phase data,
you actually find that the observations agree nicely for many of the
nearby SNe. This suggests that for most SNe, there is no justification
for assuming different errors. It is not correct that we are allowed
to play with the error because of our troubles with stretch fits.
What is wrong with just make a cut in date ? We all know that stretch does
not apply to data in the nebular phase, so why not just accepted it and
apply stretch only to pre-nebular phase data ?
Lifan
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> To: "Robert A. Knop Jr." <robert.a.knop@vanderbilt.edu>
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> Subject: Re: "Error floor"
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> I'm a little puzzled about the choice of 0.007 times the maximum flux
> point. I guess this ensures that the tails don't wag the main lightcurve
> fit, i.e. this is a way of giving a little more weight to the data near
> maximum in the cases were the later error bars are just too good for the
> errors in the tempate's tails. --Is that the goal? Perhaps we should think
> of this really as an error bar on the template (which we might know
> something about) rather than as modified error on the data?
>
>
>
> "Robert A. Knop Jr." wrote:
>
> > I'm about to go through and modify all my hamuy and riess low-z data
> > files to introduce an "error floor".
> >
> > As per our discussion, I will set a minimum error equal to 0.007 times
> > the maximum flux point in a given lightcurve data file. If any
> > lightcurve point in that data file has a flux error smaller than this, I
> > will replace that error bar with my minimum error bar.
> >
> > I think this is the procedure we agreed was best. Is there a reference
> > on why this is a good idea, so that we can skip writing the
> > justification?
> >
> > -Rob
> >
> > --
> > --Prof. Robert Knop
> > Department of Physics & Astronomy, Vanderbilt University
> > robert.a.knop@vanderbilt.edu
>
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