On Apr 8, 2007, at 7:25 PM, Michael Meyer wrote:

> Dear Dr. Chaboyer,
>
> Please find below our response to the referee report for paper
> MS# 71381 by Amaya Moro-Martin et al. entitled:
> "The Dust, Planetesimals and Planets of HD 38529".
>
> We thank the referee for his/her thoughtful comments.  We have
> addressed most of the referee's concerns, and tried to clearly
> explain ourselves in those few cases where we felt we were not
> able to adopt the referee's suggestions.
>
> We thank you for the prompt attention to our paper and look
> forward to seeing it published in the journal.
>
> Sincerely,
> Amaya Moro-Martin
>
> =========================================
>
> REFEREE:
>
> I do not think the current version of this paper is suitable for 
> publication
> in the ApJ. I hope the authors will consider the following comments as 
> they
> revise the paper. My main concern (point 4) is that the SED modeling 
> is much
> less of a constraint on the dust distribution than even the 
> acknowledged
> highly uncertain results suggest. At the end of reading this paper, it 
> really
> was not clear to me what constraints the modeling had really been 
> placed on
> the location of the IR emission beyond that provided by the initial
> back-of-the-envelope calculation (which derived 106 AU).
> The dynamical analysis is very nice, and by itself makes the paper
> worthwhile, but of course it is motivated by the observations.
>
> The list below is not by priority but rather sequentially through
> the manuscript.
>
> GENERAL RESPONSE:
>
> We thank the referee for these general comments.
>
> We agree with the referee's implication that better constraints on the
> dust/parent body location can be made from the dynamical analysis than 
> from
> the SED analysis (because of the degeneracy of the latter). In order 
> to take
> this into consideration, and to address the referee's main concern, we 
> have
> reorganized the paper in a way that the dynamical analysis motivates 
> the SED
> analysis and not vice versa.  The dynamical analysis is used first to 
> identify
> the dynamically stable niches of potential dust-producing 
> planetesimals, and
> the SED analysis is introducted afterwards, to help find out which of 
> these
> niches may actually harbor dust-producing plantesimals. The new 
> outline is
> as follows:
>
>      1. Introduction
>
>      2. Possible Location of the Dust-Producing Planetesimals:
>         Effect of Gravitational Perturbations by the Planets
>
>      3. A Collision-Dominated System: the Dust Traces the Planetesimals
>
>      4. SED Modeling
>         4.1 Single Temperature Models are Insufficient
>         4.2 Multi Temperature (SED) Models
>             4.2.1 SED Modeling Assumptions
>             4.2.2 SED Modeling Results
>
>      5. Discussion of the Dynamical and the SED Analysis
>         5.1 Location of Cold Dust
>             (this section now includes a paragraph that used to
>              be in the dynamical analysis section)
>         5.2 Upper Limits on Warm Dust
>
>      6. Conclusions
>
> The abstract and the conclusions have been reorganized accordingly.
>
> However, we do feel that the SED analysis presented in the paper is 
> important.  The "back-of-the-envelope" calculation to which the 
> referee refers is
> based on the ratio of the flux at 70 and 33 microns. Assuming blackbody
> emission, this ratio results in a dust temperature of 43 K that would
> correspond to a dust location of 106 AU.  We ellaborate on this point
> in section 4.2, where a different "back-of-the-envelope" calculation
> (based on a blackbody fit to the IRS spectra) leads a distance of 31 
> AU.
> This discrepency is what motivates the use of multi-temperature disk 
> models.
> The SED models presented in this paper (that allow for a range of dust
> temperatures) are needed to take this consideration into account.
> For example, in Figure 4, the SED agrees with a wide range of plausible
> dust disks with an outer disk radius of 50 AU and inner radii ranging 
> from
> 14 to 49 AU.  We believe it is important to investigate the possibility
> of dust located much closer to the star than 106 AU because that's
> where the planets can have a significant dynamical effect (as 
> illustrated
> in Fig. 1).  Thus we feel that the SED modelling is central to the 
> paper.
>
> We have responded to each point specifically below.
>
> REFEREE:
>
> 1. Introduction: The sample consists of the nine FEPS stars with 
> RV-detected
> planets. HD38529 is the only one with an IR excess. How does HD38529 
> compare
> in other ways (e.g., spectral type, distance, age, etc) to the other 
> stars
> in the sample anything (or nothing) special? Just a comment or two 
> would
> suffice.
>
> RESPONSE 1:
>
> The IR excess of HD 38529 was discovered as part of the FEPS project, 
> but the
> present analysis is concerned with the details of the planet/dust 
> dynamics.
> The the statistical significance of this result within the context of 
> the FEPS
> survey is addressed in  Moro-Martin et al. 2007a (April 1st ApJ).
>
> Table 1 of that paper summarizes the stellar properties of the nine 
> planet-
> bearing stars in the FEPS sample. We have added a reference to that 
> paper
> in the second paragraph of the introduction to this manuscript that
> refers to the nine planet-bearing stars in the FEPS sample.
>
> In section 3 of the previous paper (Moro-Martin et al. 2007a) we state:
>
> "Even thought it is difficult to identify statistical trends from one
> detection, it is interesting to note that HD 38529 is the most 
> luminous,
> most massive and most evolved of the planet-bearing stars in Table 1".
>
> Because the trends are not statistically significant, we prefer not to
> emphasize them by repeating them in the current paper.
>
> =========================================
>
> REFEREE:
>
> 2. Section 2, page 3: Given the total uncertainties in the flux 
> densities,
> what are the uncertainties in the calculated ?characteristic 
> temperature?
> of the dust and the corresponding calculated location? (Surely, given 
> the
> uncertainties, isn?t it naive to quote the temperature to 0.1 K and the
> location to 0.1 AU?)
>
> RESPONSE 2:
>
> We thank the referee for the suggestion.  The propagation of errors 
> lead to
> uncertainties of T = 43+/-4 K and R = 106+/-18 AU. We have included 
> these
> errors in the text (now in section 4.1 - pages 7 and 8).
>
> =========================================
>
> REFEREE:
>
> 3. Section 2, page 4: Regarding the need for multi-temperature fits to
> disk SEDs, the authors comment that ?This has been unambiguously 
> confirmed
> by the eight spatially resolved., which led Kalas (2006)? This 
> statement
> ignores the fact that multi-temperature grain distributions were shown
> before Kalas (2006) by several studies to be essential in disks. This
> omission should be corrected. Consider the following examples (but 
> there
> are others):  for Beta Pic (Li & Greenberg 1998, A&A, 331, 291; Telesco
> et al. 2005, Nature, 433, 133), for HR4796A (Li & Lunine 2003, ApJ, 
> 590,
> 368), for Eps Eri (Li, Lunine, Bendo 2003, ApJ, 598, L51). Also, I 
> think
> all the examples are young debris disks, but isn?t HD 38529?s much 
> older?
> Is that a problem? The paper does not even touch on the issue of the 
> age
> of the disk and how the usual archetypes may or may not be appropriate 
> for
> comparison.
>
> RESPONSE 3:
>
> The four references suggested by the referee have been included in the 
> text
> (section 4.1 in the revised manuscript). With regard to the ages, HD 
> 53143 and
> HD 139664 are old disks, with ages of approximately 1 and 0.3 Gyr,
> respectively. HD 53143 shows a radial extend > 55 AU, while HD 139664 
> shows a
> belt-like morphology.  Kalas et al. (2006) pointed out that there is a
> "significant diversity in the radial architecture of debris disks that 
> appear
> unconnected to stellar spectral type or age." We believe the concensus 
> to date
> is that disks can be wide or narrow and the modeling should explore 
> those
> options, regardless of the age estimates, which are usually uncertain.
>
> =========================================
>
> REFEREE:
>
> 4. Section 2.1: Since the SED analysis in this paper forms the basis 
> for
> any conclusions about the disk geometry, the assumed dust properties 
> are,
> as the authors note, important for determining the model results. Why,
> therefore, do they not consider a broader range of particle properties
> than, apparently, just silicate Mie spheres? In my opinion, it is not
> sufficient to just comment (as is done in footnote 3) that the 
> dependence
> of the SED on grain composition is discussed elsewhere (note, e.g., the
> exhaustive analysis considered by Li and collaborators in some of the
> references in comment 3, above). It should be discussed here in the
> context of this object. What is the uncertainty in the deduced source
> geometry introduced by the ranges in possible grain properties (e.g.,
> composition, porosity, sizes)? Also, might we not expect the dust to
> be different for this post-ms-star disk compared to that for ms debris
> disks? Perhaps telling us more about the star (composition, age, etc.)
> might be useful here.
>
> RESPONSE 4:
>
> We appreciate the referee's point.  The reason why the SED analysis is
> considering only basic grain properties (spherical grains and 
> "astronomical
> silicate" composition) is mainly because the constraints on the excess
> associated with HD 38529 are limited to a detection at 70 microns 
> (that is
> not spatially resolved) and a spectrum that shows a slight rise at the
> longest wavelengths (>30 microns). The system is not detected at 160 
> microns
> and the other Spitzer bands only detect the photosphere of the star. 
> More
> sophisticated modelling would require additional observational 
> constraints,
> available for the systems to which the referee refers (e.g. Beta Pic,
> HD4796A, Eps Eri).  We agree with the referee that the SED analysis in 
> the
> case of HD 38529 is very degenerate and should not be the main basis 
> of the
> paper conclusions.  However, we feel additional modelling is not 
> worthwhile.
>
> =========================================
>
> REFEREE:
>
> 5. Top of page 5: the blowout radius is calculated to be 2.26 microns.
> Given all the uncertainties, should one really quote it to that 
> precision?
>
> RESPONSE 5:
>
> We thank the referee for this comment. We have changed it to 2 microns.
>
> =========================================
>
> REFEREE:
>
> 6. Page 5, second full paragraph (?The outer radius..?): As also noted
> above, given that HD38529 is a post-ms star, don?t the authors have
> some reservations or caveats that they want to air regarding this
> comparison with all these really young disks (e.g., disks in the center
> of the Trapezium!)? Maybe just use the Kuiper Belt, even if we still 
> don?t
> know the details of its dust distribution? At least, it is older than
> the other listed stars. I?m not claiming one can?t or shouldn?t make
> this comparison, but I do think it seems more than a little suspect
> unless one acknowledges the disparity and justifies the comparison.
>
> RESPONSE 6:
>
> We thank the referee for this suggestion.  We have deleted the 
> sentences
> referring to the younger disks.
>
> =========================================
>
> REFEREE:
>
> 7. Starting at top of page 7: This paragraph, which is intended to help
> the reader understand the model results, is really not usefully
> comprehensible. It is not an explanation but rather just putting some
> equations into words. Phrases such as ?emission from the outermost 
> radii
> of the RJ regime? and ?is increased by nu^2 but decreased by r^3/2? and
> reference to the ?log interval of radius? are not illuminating. In my
> opinion, this whole paragraph should be rewritten so that it reads as a
> real verbal explanation of the modeling results rather than an exercise
> in numerology (I doubt that the authors would really explain their 
> results
> to colleagues in the hallway or at a workshop in the manner this 
> paragraph
> is written).
>
> RESPONSE 7-A:
>
> We thank the referee for this insight.  We have tried to simplify this
> paragraph as the referee suggests.
>
> =========================================
>
> REFEREE:
>
> As another trivial example, near the bottom of page 7, small
> grains are excluded by the modeling?but that?s because there?s no 
> detectable
> 10-micron emission, which would arise in smallish particles, right? If 
> so,
> can?t that just be stated? (This is, I think, a conclusion 
> strengthened by
> the lack of a detectable silicate feature, but that assumes that this
> post-ms disk is indeed composed of silicates, which hasn?t be justified
> explicitly.)
>
> RESPONSE 7-B:
>
> We thank the referee for this comment.  The argument about the lack of 
> a
> significant population of small grains in HD 38529 is based primarily
> on the lack of a continuum excess emision between 10--20 microns, as 
> the
> IRS spectra only shows photospheric emission at wavelengths shorter 
> than
> 30 microns. We have added explicit discussion of this to the text for
> clarification.  It is true that for other debris disks, where there is
> a warm dust at higher temperatures, but no 10 micron silicate feature,
> the argument for the lack of small grains is indeed the one the referee
> describes (e.g. Jura et al. 2004).
>
> =========================================
>
> REFEREE:
>
> 8. Page 8: The comment that ?the presence of inner cavities has been
> unambiguously comfirmed? is supported in the text by a list of 
> references
> that is incomplete and misleading and should be augmented. For example,
> Beta Pic was first shown clearly to have a central cavity (in the
> mid-infrared) by Lagage & Pantin (1994, Nature 369, 828), and HR 4796A
> was first shown to have a cavity by Koerner et al. (1998), Schneider et
> al. (1999) and Telesco et al. (2000). Also, how sure are the authors 
> that
> this post-ms disk is gas free? Might we not expect mass loss from the 
> star
> to complicate this simple assumption? Some comment, however brief, 
> seems
> necessary.
>
> RESPONSE 8:
>
> We thank the referee for this comment.  Due to the reorganization of 
> the
> paper, the paragraph to which the referee is referring to has been 
> deleted
> (the section on inner cavities was meant to provide the link between 
> the SED
> and the dynamical analysis, but is no longer needed).  We feel that the
> interesting speculation concerning gas due to post-main sequence 
> mass--loss
> is beyond the scope of this paper.
>
> =========================================
>
> REFEREE:
>
> 9. A general comment on Section 4.2: the dynamical analysis presented 
> in
> this section is well described and very interesting and, by itself, 
> makes
> the paper worth publishing. It tells us where the dust may be, but, in
> view of the stated and unstated uncertainties in the SED modeling, it 
> does
> not seem to me to be particularly informed or constrained by the SED
> analysis, despite the suggestion that it is (end of first paragraph, 
> p. 13).
> I certainly do agree with the last paragraph of the paper: direct 
> images are
> needed to break the ?degeneracy? of the SED models.
>
> RESPONSE 9:
>
> We thank the referee for this important suggestions.  The paper has 
> been
> reorganized to address this point (please see RESPONSE GENERAL above).
>
> =========================================
>
> Additional changes:
>
> - We have deleted Fig. 6 in the new version of the paper (this is the 
> figure
> with the schematic illustration of the results). We think the 
> description
> of the results is sufficiently explained in the text and there is not 
> really
> the need for an extra figure.
>
> - We have deleted Table 2 with the summary of the SED modeling results.
> This table provided the same information that is shown more clearly in 
> Fig. 4.
>
> ---------------