Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Chromospheric Models and the Oxygen Abundance in Giant Stars   Realistic stellar atmospheric models of two typical metal-poor giant stars in
Omega Centauri that include a chromosphere influence the formation of optical
lines of Oxygen I: the forbidden lines (630nm, 636nm) and the infrared triplet
(777.1-777.5 nm). One-dimensional semi-empirical non-LTE models are constructed
based on observed Balmer lines. A full non-LTE formulation is applied in
evaluating line strengths of O I including photoionization by the Lyman
continuum and photoexcitation by Ly-alpha and Ly-beta. Chromospheric models
(CHR) yield forbidden oxygen transitions that are stronger than in
radiative/convective equilibrium (RCE) models. The triplet oxygen lines from
high levels also appear stronger than produced in an RCE model. The inferred
oxygen abundance from realistic CHR models for these two stars is decreased by
factors ~3 as compared to values derived from RCE models. A lower oxygen
abundance suggests that intermediate mass AGB stars contribute to the observed
abundance pattern in globular clusters. A change in the oxygen abundance of
metal-poor field giants could affect models of deep mixing episodes on the red
giant branch. Changes in the oxygen abundance can impact other abundance
determinations critical to astrophysics including chemical tagging techniques
and galactic chemical evolution.

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The categories of this paper are: nucl-th
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The categories of this paper are: adap-org
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The categories of this paper are: chem-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph
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The categories of this paper are: stat
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The categories of this paper are: chao-dyn
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The categories of this paper are: mtrl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: math
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The categories of this paper are: physics
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The categories of this paper are: q-bio
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The categories of this paper are: supr-con
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The categories of this paper are: nlin