From: Andy Howell (DAHowell@lbl.gov)
Date: Wed Apr 30 2003 - 17:35:57 PDT
Rob et al.,
This comment falls into the "Something we need to deal with before we
submit the paper"
category. Sorry to bring this up at such a late date, but I never
looked closely at the
spectroscopy of the 11 new SNe because you assured me that (a) someone
had signed off on
them, and (b) you weren't going to throw them out anyway.
But now I have looked at the spectra in the interest of providing you
with some text.
Most of the spectra are Ia's -- I think Peter gave you a list of the
ones with evidence
for a Si II line at 4000A.
But three others don't have a Si II line. I don't see good evidence for
a Si line, or
SII for: 1997ez (97226), 1998ay (98104), 1998be (9878).
After running my program on these three, it is clear that 97226 is a Ia
(a Ia matches great, and nothing else does), but the other two aren't as
clear
Many things match, and a Ia doesn't look better than anything else.
You can see comparison's of my plots, Isobel's original plots, and the
data here:
http://supernova.lbl.gov/~howell/robpaper/index.html
"Epoch" gives the date that the spectrum was taken relative to the LC max.
Peter has seen these plots and he agrees with me that 98104 and 9878 are
suspect.
I'm not even sure how 9878 and 98104 got included in the list of Ia SNe.
SNTrak only lists 98104 as a SN (not a Ia). It says: "SN features a
little scary."
Somehow, it the circular it became listed as "Ia" but I can't figure out
the reason why.
The spectrum doesn't look like a Ia.
SNTrak lists 9878 as Ia, but not definitively so, "Spectrum seems that
it could be a Ia. Isobel should
set the type and typeconf."
The ps plots on the web page that were done in 1998 used Isobel's IDL
program to subtract off
an arbitrary amount of E galaxy. From experience, I have learned that
you can make not-necessarily
Ia things look like Ia's using this technique. Due to the E's 4000A
break, you subtrack off more
light blueward of 4000A than redward, and this can mimic Ca from the
SN. Furthermore, this can
change the slope to make something match a Ia. My program is more
sophisticated, and it doesn't
show better fits for Ia's than II's or Ib/c's for either of these SNe.
I am not saying it is not possible that these are Ia's -- I am just
saying that we can't say these
are certainly spectroscopically confirmed as Ia's.
There are a few ways to proceed:
(1) Throw out these two SNe in some fit. But since I'm sure you aren't
going to do that, we can also...
(2) See if Eric has more final reductions of these SNe. Isobel's
reductions were preliminary.
(3) Check to see if either is in an E galaxy. Neither are in the
Sullivan paper. The images
that Quimby shows aren't conclusive to me. Isobel's spectra notes say
that the host of 9878 shows
Ca H & K, so maybe it is in E, but the host of 98104 has OII, OIII, so
maybe it isn't.
(4) Peter is going to check the colors of the SN tonight to see if we
can say anything about them.
If we can't figure out anything else we can just say that the spectra
are "consistent" with a Type Ia SN,
(though they are "consistent" with anything), and say that the LCs match.
Here is the info on what the other non-VLT spectra show:
IAU SCP 4000 6150 SII
1997ek 97201 y n n
1997eq 97198 y n y
1997ez 97226 n n n
1998aw 9855 y y? y?
1998ay 98104 n? n n
1998be 9878 y? n n
1998bi 98142 y n n
-Andy
clidman wrote:
> Here is a short table that summarizes the ESO observations and IDs.
> IAUC Alternative z Inst. + Tel. Mode Redshift
> based on SiII 6150 SiII ~4000
> =============================================================================================================
> 1998as 98122 0.355 EFOSC2 + ESO 3.6m Visitor [OIII]
> H_beta, H_alpha in host Yes Yes
> 1998ax 98109 0.497 EFOSC2 + ESO 3.6m Visitor [OII] in
> host Yes Yes
> 1998ba 9819 0.43 EFOSC2 + ESO 3.6m Visitor
> Supernova No Yes
> 2000fr Beethoven 0.543 FORS1 + Antu (VLT-UT1) Service [OII] in
> host No Yes
> =============================================================================================================
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