From: clidman@eso.org
Date: Thu Jan 15 2004 - 13:40:51 PST
Dear Serena,
Thanks for the notes. I have a couple of comments.
>
> 5) Spectral templates: Nobili vs Knop templates. Differences in
> K-corrections from J-band to rest frame I-band are about 0.05 mag. This
> is very small and it is not limiting the analysis presented in this
> paper.
>
It might be small, but this 0.05 magnitude should be quoted as a
systematic error.
> 6) Definition of J band photometric system: 0.05 mag systematic
> uncertainty estimated by Chris Lidman by comparing the Person J to
> Bessel and Brett J. See document linked Chris'web page for discussion
> (usual SCP username and passwd):
>
I talked to Mike Bessell about this point and the reasoning behind the
error is that although the primary standard (Vega) is well measured in both
the IR and the optical, with errors of less than 1%, the fainter
IR and optical standard star systems, which are tertiary standards at
best, have been developed independently. Hence, it is not unreasonable
to expect some divergence as one goes from the primary standard to
the tertiary standards. Mike thought that 0.05 was too conservative and
suggested 0.03 magnitudes as a likely error.
Experimentally, there are several ways this error can be estimated. The
easiest way is to observe a set of A0 stars in both the IR and optical.
By definition, V-J = 0. It should be possible to use the 2MASS
point source catalogue to do this and this is something that I will do
when I return to Santiago on the 23rd.
Cheers, Chris.
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