From: Serena Nobili (serena@lpnhep.in2p3.fr)
Date: Thu Dec 16 2004 - 07:38:06 PST
Dear Vitaliy,
as you know I am also working on my own on this issue and I can probably
help in messing up even more this complicated topic. I want to stress,
however, once again I am using the *real* data to compute the colours and
not the results of a lightcurve fit (the same as in Nobili et al 2003), as
I believe is the case of all the plots you put in the wiki. Moreover, I
am fitting a linear relation of colours with the B-band stretch. My
finding, however, is similar to yours:
(U-B)_tBmax = -0.47 for s(B)=1
The attached plot shows the result of my fit in a time bin of -1<t<1 days.
The fit is actually done on the whole time and stretch together,
e.g. without binning the data. The plot has been made only for comparison
with yours. Also, as I said above, the points plotted are the real data,
only for SN which were observed both in U and B at the same epoch (the two
points at the same stretch value are the same SN observed twice in this
time interval).
I have some questions and comments about your plots, in particular U-B vs
S(U). First, the exponential function you fit on the plot is mainly
determined by the point at very low stretch (s ~ 0.6) which I believe is
sn1997cn. Is this correct? If you take that point away, a linear relation
would work quite well to fit the data. I am personally not including this
SN in the analysis, also due to the difference of 0.15 mag , also
discussed by Jha in the thesis, with the U-band published by Turatto et
al. for the same SN.
On the same line, there is another object, SN1997bp, whose U-band was
published by Altavilla et al 2004 (same group as Turatto), for which the
discrepancy with Jha is ~0.2-0.3 mag. So, it might be dangerous to include
this SN in your fit. Other 2 SNe, SN1997br and SN1999aa, also observed in
U-band by Altavilla et al. are quite in agreement with Jha's
measurements.
I hope I helped the discussion.
Cheers,
Serena
PS. I apology for sending the file instead of adding it in the TWiki
page. I tried to register, but it does not like my name so I was unable to
do so (although I did use SerenaNobili). Can someone help me with that?
On Wed, 15 Dec 2004, Vitaliy Fadeyev wrote:
>
>
> Dear SCPers,
>
> the following TWiki page describes a color treatment for Albinoni analysis.
> Since the topic is relevant for other on-going analyses, and also
> because there
> is a difference with the color assumed in Knop 03 paper, we call your
> attention
> to the issue, and solicit feedback.
>
> Direct link to TWiki page:
> http://supernova.lbl.gov:8080/twiki/bin/view/Albinoni/ANoteOnColor
>
> Instruction on how to access the SCP TWiki are here:
> http://supernova.lbl.gov/collab/
>
> Cheers,
> vitaliy
>
>
>
>
>
------------------------------------------------------------------------ http://supernovae.in2p3.fr/~serena/ Tel +33 1 44277329
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