Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Comments on the manuscript: ``The weak absorbing outflow in AGN Mrk 279:
  evidence of super-solar metal abundances'' astro-ph/0611578 by Fields et al   A recent manuscript posted on astro-ph (astro-ph/0611578) by Fields et al.
(hereafter F06) reports evidence of supersolar metal abundances in Mrk 279 by
analyzing its Chandra LETGS X-ray spectrum. We point out that it is impossible
in principle to obtain direct metal abundances from these X-ray data, since
there is no handle on the amount of hydrogen column density. If F06 would have
lowered their C, N, O and Fe abundance by a factor of ten and increased the
hydrogen column density by a factor of ten, they would have obtained an almost
identical fit with subsolar metalicity. F06 find support for their supersolar
metal abundances from a cursory analysis of the UV data from the same Mrk 279
campaign. We point out that F06 included in that analysis portions of the UV
trough that are known to arise from gas unrelated to the outflow, which weakens
the support from the UV data. A detailed analysis of the Chandra LETGS X-ray
spectrum was accepted for publication in A&A on Sept 14 2006 (Costantini et al
2006; hereafter C06) and posted on astro-ph on the same date. F06 ignore most
of this published analysis while duplicating the finding of two ionization
components with similar parameters to the ones found by C06. Finally, we note
that it is possible to derive accurate abundances from the UV data set of this
object. We already published these findings in a conference precedings and have
submitted the relevant manuscript to ApJ. We find that relative to solar the
abundances in the Mrk 279 outflow are (linear scaling): carbon 2.2 +/- 0.7,
nitrogen 3.5 +/- 1.1 and oxygen 1.6 +/- 0.8.

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The categories of this paper are: dg-ga
33
The categories of this paper are: plasm-ph
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The categories of this paper are: adap-org
5
The categories of this paper are: gr-qc
3
The categories of this paper are: physics
16
The categories of this paper are: stat
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The categories of this paper are: ao-sci
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The categories of this paper are: supr-con
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-bio
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The categories of this paper are: nlin
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The categories of this paper are: quant-ph
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The categories of this paper are: q-alg
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-th