Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Model Photospheres for Late-Type Stars from the Inversion of
  High-Resolution Spectroscopic Observations. Groombridge 1830 and Epsilon
  Eridani   An inversion technique to recover LTE one-dimensional model photospheres for
late-type stars, which was previously applied to the Sun (Allende Prieto et al.
1998), is now employed to reconstruct, semi-empirically, the photospheres of
cooler dwarfs: the metal-poor Gmb1830 and the active star of solar-metallicity
Eps Eri. The model atmospheres we find reproduce satisfactorily all the
considered weak-to-moderate neutral lines of metals, satisfying in detail the
excitation equilibrium of iron, the wings of strong lines, and the slope of the
optical continuum. The retrieved models show a slightly steeper temperature
gradient than flux-constant model atmospheres in the layers where log tau <=
-0.5. We argue that these differences should reflect missing ingredients in the
flux-constant models and point to granular-like inhomogeneities as the best
candidate.
  The iron ionization equilibrium is well satisfied by the model for Gmb1830,
but not for Eps Eri, for which a discrepancy of 0.2 dex between the logarithmic
iron abundance derived from neutral and singly ionized lines may signal
departures from LTE. The chemical abundances of calcium, titanium, chromium,
and iron derived with the empirical models from neutral lines do not differ
much from previous analyses based on flux-constant atmospheric structures.

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The categories of this paper are: q-alg
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The categories of this paper are: hep-th
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The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: physics
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The categories of this paper are: supr-con
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The categories of this paper are: hep-lat
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The categories of this paper are: econ
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The categories of this paper are: ao-sci
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The categories of this paper are: eess
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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: hep-ex
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The categories of this paper are: acc-phys
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The categories of this paper are: cond-mat