From: Robert A. Knop Jr. (robert.a.knop@vanderbilt.edu)
Date: Sat Mar 27 2004 - 20:04:18 PST
On Sat, Mar 27, 2004 at 11:46:11PM -0400, Chris Lidman wrote:
> The 0.1 magnitudes comes from Lifan's analysis of ~500 spectra - no
> don't jump! I am assuming that Lifan got this part of the analysis
> correct. The 0.05 magnitudes we had used before came from comparing a
> much smaller number of spectra, basically yours and Rob's. I feel that
> the 0.1 magnidues estimated by Lifan is more secure estimate of the
> scatter.
Did Lifan give that scatter, or is that based on an offset between Lifan
and what Serena did?
Before I'd trust this at all, I'd want to know more about Lifan's
analysis.
For instance, from what I know about what he's done, it's entirely
possible that he's taken a supernova spectrum and applied a reddening
law to get the B-V color right. (This is the sort of thing that Peter
used to do.) In other words, any continuum calibration out in the R and
I may be extrapolated, with a potential corresponding increase in
scatter. Until I know more about what Lifan did, I don't even want to
trust that part of the analysis. His estimate could be an overestimate.
Now if he did do something careful to maintain continuum levels in R and
I, then, sure, that part of the analysis may be fine. But I haven't
seen nearly enough about his analysis to believe that yet.
-Rob
-- --Prof. Robert Knop Department of Physics & Astronomy, Vanderbilt University robert.a.knop@vanderbilt.edu
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