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mazzali@ts.astro.it, deng@astron.s.u-tokyo.ac.jp
From: "Koji S. Kawabata" <koji.kawabata@nao.ac.jp>
Subject: Revised paper of spectropolarimetry on SN 2002ap
Cc: jeffery@kestrel.nmt.edu
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Status: R
Dear all,
David and I have prepared the response and revised the paper.
The former is attached to this e-mail, and the latter can be retrieved from
http://optik2.mtk.nao.ac.jp/~kawabtkj/tmp/ms.tex (TeX source)
http://optik2.mtk.nao.ac.jp/~kawabtkj/tmp/ms.ps (PS file with color figures)
The editorial staff says that the estimated length of the current paper
exceeds 4 journal pages. However, the paper has already been highly
balanced and I would not like to cut any further. (Please see below.)
I am planning to submit it on Sep. 25 (JST).
I am sorry to bother you, but please tell me comments on them by Sep. 24 (UT)
or 25 (JST).
Sincerely yours,
Koji S. Kawabata
---
Dear Dr. Dalgarno,
This is the response to the third referee's report received on
September 20.
We still consider this paper for publication in Part 2 (Letter)
without further reduction of the paper length, but we will readily
agree to publication in Part 1 (Main Journal) when the publication
in Part 2 is found to be impossible.
Sincerely yours,
Koji S. Kawabata
PS
The institution responsible for page charges of this Letter is
National Astronomical Observatory of Japan
Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan
TEL: +81-422-34-3533 FAX: +81-422-34-3545
--------------------------------------------------------------
Outline of the revisions:
Sep. 25, 2002
We have made revisions in response to the referee's
suggestions. We describe below the detail of our revisions,
in which the related referee's comments are cited using '>'
symbols.
> o When discussing the jet hypothesis, I am surprised and a
> bit puzzled that mention is not made of the recent work by
> Craig Wheeler et al. (e.g., Wheeler, Meier, \& Wilson 2002),
> who propose that "bipolar" jets may be responsible for the
> ejection of envelopes in core-collapse SNe. When reading
> Kawabata's jet hypothesis, in fact, my initial assumption
> was that there were *2* jets, and I could not understand why
> reflection off of *both* concentrations of material was not
> discussed. It was only after reading for a second time that
> I inferred that there was only 1 clump of material. The
> authors need to make this clear from the start: they are
> discussing the possibility of only *1* blob of material.
> Clearly a second clump, if ejected in the opposite direction,
> would have consequences on the observed polarization (except
> I suppose for i=90). While I think it is OK to limit the
> simple model to a single blob of material, I feel that this
> assumption should be made very clear to the reader, and that
> the Wheeler et al. work should at least be referred to as
> further support for jets in core-collapse SNe.
The referee's suggestion is reasonable. Our model supposes a
single jet component. We did this as a simplifying assumption
in a first analysis. If second clump was ejected in the
opposite direction, a more complicated model of the jet
polarization would be needed unless the jets were at angles
90 degrees or 0/180 degrees to the line of sight.
(In the latter case, the component ejected almost along the
line of sight toward us would produce nearly-non-redshifted
and unpolarized scattered light which not be detected in
polarimetry, but perhaps in flux spectra.)
We clarify our assumption with a parenthetical remark in
section 4.3 as following,
(We assume a single jet or clump for simplicity here, although
a pair of bipolar jets are physical possibility (e.g.,
citet{whe02}).)
> o I do not understand exactly how the "residual polarization"
> that is shown in Fig. 3e and discussed at the bottom of p. 7,
> is derived. It seems that the authors wish to remove the
> effect of the proposed jet polarization from the Feb. data,
> and then show that what remains in the Feb. data is consistent
> with the P.A. of the March data, but it is not clear to me how
> is this done. What is the assumed value of the "jet
> polarization"? I had thought that this value would simply be
> the continuum polarization at some particular wavelength, but
> since the "residual" is at least somewhat greater than 0
> (even in the 5000-7000 A range), I am lead to believe that
> this is not so.
> Was it taken to be some arbitrarily-defined fraction of the
> observed polarization? Is there a wavelength-dependence to
> it? The authors need to make clear exactly what is going on
> here.
As the referee mentioned, the `residual polarization' is derived
from the Feb. data.
We obtain the residual polarization by subtracting jet
polarization Stokes parameters from intrinsic polarization
Stokes parameters.
The jet Stokes parameters are
q_jet = p_jet * cos( 2 * 80 deg ) and
u_jet = p_jet * sin( 2 * 80 deg )
which we obtain from
p_jet = f * ( F' / F ),
where f is a scale factor of 0.0018, F is the flux of
the central star, F' is the redshifted F by 0.23c, and
PA=80 degrees is postion angle of the jet polarization.
The parameters $p_jet$, $f$, $0.23c$, and $PA$ were specified
in section 4.3.
We clarify this point in section 4.3 with the sentence
``To test this model we have eliminated the jet polarization
component from the February intrinsic polarization by
subtracting jet polarization Stokes parameters from the
intrinsic polarization Stokes parameters.''
> o SN 2002ap is currently a very "hot" object, with new
> references being added to the literature on an almost
> bi-weekly basis. Although I don't recommend including all
> (or even most) of the latest references, I do feel that two
> should be referenced that are not, especially since they
> are now (according to ASTRO-ph and the journal's web sites)
> accepted and would be useful to readers to look at:
> o Kinugasa et al. (ApJL; astro-ph/0208470) -- Presents
> detailed modeling of the spectral evolution of SN 2002ap.
> This is very relevant to the discussion of ejecta velocity.
> Perhaps this work could be referenced on p. 8, first
> complete paragraph, where the "maximum ejecta velocity
> indicated by spectrum synthesis of SN 2002ap" is given to
> be 0.22c; as it is, I'm not sure where this number comes
> from. For photospheric velocity, Kinugasa find v=35,000
> km/s early on.
Kinugasa et al. show the photospheric velocity and its time
variation in the early phase. Their result is clear, and
helpful for the discussion of our Letter as the referee
suggests. The `maximum ejecta velocity' of 0.22c is quoted
from Mazzali et al. (2002), which is referred in the previous
sentence. We have cited Kinugasa et al. and clarified the
sentence.
> o Leonard et al. (PASP; astro-ph/0206369) -- Presents
> similar spectropolarimetric data to Kawabata et al.,
> although with somewhat different interpretation.
> Referencing this work is complicated by the fact that the
> most relevant part of it to this paper is a *reaction* to
> the jet model described here, and put on astro-ph earlier.
> Although not discussed in any detail, Leonard et al.
> demonstrate a similarly good fit (perhaps better, even)
> between the early-time polarized flux and redshifted flux,
> a comparison that may enhance belief in the jet model
> presented by the present paper. I leave it to the author's
> discretion whether to refer to this paper; if they choose
> to do so, they should make it clear that the jet model
> originated in the present work, and that Leonard et al.
> is testing the comparison for a similar data set.
Leonard et al.'s paper uses data independently obtained at the
same epochs as ours: it is useful for readers to see that data
too. Since that paper has been accepted earlier, it is best to
clarify the originator of the redshifted flux idea. Therefore,
we have cited that paper in the text.
> For the record, I agree with the authors that the Berger
> et al. ApJL (astro-ph/0206183) need not be referenced.
> That article unfortunately makes only one glib, broad
> statement about the production of radio emission from a
> jet, and does not in my mind effectively refute the jet
> hypothesis.
> o Minor point: When discussing the "reverse P-Cygni"
> polarization profile, the authors may want to include a
> reference to Leonard & Filippenko (2001, PASP, 113, 920),
> since that paper presented and took the Jeffery (1991a,b)
> model to a somewhat more analytical level.
The referee's suggestion is reasonable because of Leonard &
Filippenko's (2001, PASP, 113, 920) useful analysis,
observations of line polarization, and discussion of
interstellar polarization. We have cited that paper in the text.
> o Picky point: Bottom of p. 6, 4th line from the bottom.
> "cf" should be replaced by "see", since "cf" means "contrasts
> with" (as I've been told by multiple ApJ editors over the
> years).
We reworded the "cf." to "see", following the referee's suggestion.
> o p. 7, 5th line. The authors are quite clear that their
> proposed jet model is only speculative at the moment.
> However, such warnings can evidently not be overemphasized.
> I think the sentence "This agreement suggests...explosion."
> should be reworded as: "This agreement suggests, but does
> not prove, that a large component of polarized flux may
> come from ..."
The referee's suggestion is reasonable and we rephrased the
sentence, following it.
--------------------------------------------------
Koji S. Kawabata E-mail: koji.kawabata@nao.ac.jp
Optical and Infrared Astronomy Division,
National Astronomical Observatory of Japan
TEL: +81-422-34-3533 FAX: +81-422-34-3545
--------------------------------------------------