From: Rollin Thomas (rthomas@panisse.lbl.gov)
Date: Mon Dec 22 2003 - 15:03:10 PST
Gabriele,
I have been looking over your SN 1999ac paper and I have some pretty
general comments to give you at this time, and I hope you will be able
to give me the opportunity to send my more detailed comments to you in
one week. I would do it for you sooner, but I will be out of town
(and believe it or not, away from the Internet) from the 24th until
the 29th. I can promise you a very detailed set of comments when
I come back, though. Then we can maybe have a back-and-forth kind
of discussion to shape things up?
Clearly the most important result of this analysis is the pretty good
identification of C II and perhaps the C III at early times. That's a
very good use of Synow. The focus on the C identification is there in
the paper, but I think its framing in Section 1 needs a bit of work.
Finding C in a SN Ia is about as important as it gets for models, so a
more clear discussion of the background would help. For example, I
notice that you've got the appropriate references for W7, but for the
parallel discussion on DD models you haven't got any, and you leave
out some important models. Perhaps it would help your understanding
to if you went back and took another look at what papers were
appropriate to put here?
I am concerned about your classification of 1999ac as 1999aa-like (I
take you to mean in the Li et al sense). First you make this claim
and then I look at Figure 3 and I'm not convinced. Without plotting
them myself, I tend to think that the blue of 1999ac looks a lot like
1990N, and then in the red, somewhere in between. Maybe this is what you
mean by 1999aa-like, but then again I am confused. I guess my point
here is that you should take a long hard, honest look at that figure
and see if you know what I am talking about. I'm happy to find out
if you think I am wrong, I just want to know more about why you think
this way.
What I'd like also is if (somewhere) you could define precisely what you
mean by peculiar, if for no other reason than to educate readers not
really familiar with the Li/Branch debate over the peculiarity rate.
You do reference papers, but the definition needs to be included for
the purposes of depth.
Also, I think it's perfectly acceptible to include fits to the entire
spectral range of the supernova for just one ion, or for all the other
utilized ions minus one to prove a point. Close-ups are good in some
cases, but often I want to see how things look spectrum-wide. I am
pretty sure David's got examples of this throughout his catalogue of
fits.
And again (I admit I haven't read some of the later part of the paper
very carefully) I want to emphasize that we can't determine the
envelope structure, we can only constrain it. So I'm always a little
suspicious of figures like #14 that purport to represent the
composition without the following caveat: There's a temperature
structure that Synow can only constrain very weakly, and it requires
auxiliary code to improve on that.
Oh, and I've got some 1998aq spectra you might want to look at. I got
them through David, and they are supposed to be going up on Suspect
soon (in which case it would be legitimage for you to use them; they
are public then). You could do your minimum fitting routine on it
and include those data in your velocity plots. (Incidentally, how
automated is the code you use to do this? This is the Levenberg-
Marquardt code you used in the previous paper? Do you need something
so complicated for this? Too interesting: I digress...)
I apologize for not having had the opportunity to give you better
comments at this time, I know how it is when you are waiting on
comments from people. But I promise if you give me until Tuesday or
so of next week I can do a much better job.
Of course if you have any questions about my comments here, or in
general, you can just email me. It will just take me longer to get
back to you once I am out of town.
Sorry again,
Rollin
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