Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fundamental Parameters and Abundances of Metal-Poor Stars: The SDSS
  Standard BD +17 4708   The atmospheric parameters and iron abundance of the Sloan Digital Sky Survey
(SDSS) spectrophotometric standard star BD +17 4708 are critically examined
using up-to-date Kurucz model atmospheres, LTE line formation calculations, and
reliable atomic data. We find Teff = 6141+-50 K, log g = 3.87+-0.08, and
[Fe/H]=-1.74+-0.09. The line-of-sight interstellar reddening, bolometric flux,
limb-darkened angular diameter, stellar mass, and the abundances of Mg, Si, and
Ca are also obtained. This star is a unique example of a moderately metal-poor
star for which the effective temperature can be accurately constrained from the
observed spectral energy distribution (corrected for reddening). Such analysis
leads to a value that is higher than most spectroscopic results previously
reported in the literature (~5950 K). We find that the ionization balance of Fe
lines is satisfied only if a low Teff (~5950 K) is adopted. With our preferred
Teff (6141 K), the mean iron abundance we obtain from the FeII lines is lower
by about 0.15 dex than that from the FeI lines, and therefore, the discrepancy
between the mean iron abundance from FeI and FeII lines cannot be explained by
overionization by UV photons as the main non-LTE effect. We also comment on
non-LTE effects and the importance of inelastic collisions with neutral H atoms
in the determination of oxygen abundances in metal-poor stars from the 777 nm
OI triplet. (Abridged)

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The categories of this paper are: patt-sol
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The categories of this paper are: quant-ph
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The categories of this paper are: math
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The categories of this paper are: gr-qc
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The categories of this paper are: q-fin
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The categories of this paper are: adap-org
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The categories of this paper are: ao-sci
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The categories of this paper are: dg-ga
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The categories of this paper are: funct-an
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The categories of this paper are: physics
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The categories of this paper are: econ
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The categories of this paper are: alg-geom
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The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-bio