Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: NLTE carbon abundance determination in selected A- and B-type stars and
  the interpretation of C\ione\ emission lines   We constructed a comprehensive model atom for C\ione\ -- C\ii\ using the most
up-to-date atomic data available and evaluated the non-local thermodynamic
equilibrium (NLTE) line formation for C\ione\ and C\ii\ in classical 1D models
representing the atmospheres of A and late B-type stars. Our NLTE calculations
predict the emission that appears at effective temperature of 9250 to 10\,500~K
depending on log~$g$ in the C\ione\ 8335, 9405\,\AA\ singlet lines and at
\Teff~$>$~15\,000~K (log~$g$ = 4) in the C\ione\ 9061 -- 9111\,\AA\,, 9603 --
9658\,\AA\, triplet lines. A prerequisite of the emission phenomenon is the
overionization-recombination mechanism resulting in a depopulation of the lower
levels of C\ione\ to a greater extent than the upper levels. Extra depopulation
of the lower levels of the transitions corresponding to the near-infrared
lines, is caused by photon loss in the UV lines C\ione\ 2479, 1930, and
1657\,\AA. We analysed the lines of C\ione\ and C\ii\ in Vega, HD~73666,
Sirius, 21~Peg, $\pi$~Cet, HD~22136, and $\iota$ Her taking advantage of their
observed high-resolution spectra. The C\ione\ emission lines were detected in
the four hottest stars, and they were well reproduced in our NLTE calculations.
For each star, the mean NLTE abundances from lines of the two ionization
stages, C\ione\ and C\ii, including the C\ione\ emission lines, were found to
be consistent. We show that the predicted C\ione\ emission phenomenon depends
strongly on whether accurate or approximate electron-impact excitation rates
are applied.

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The categories of this paper are: hep-ph
4
The categories of this paper are: cond-mat
30
The categories of this paper are: q-alg
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The categories of this paper are: q-bio
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The categories of this paper are: eess
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The categories of this paper are: hep-lat
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The categories of this paper are: math
29
The categories of this paper are: funct-an
26
The categories of this paper are: bayes-an
35
The categories of this paper are: mtrl-th
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-th
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The categories of this paper are: adap-org
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The categories of this paper are: chao-dyn
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The categories of this paper are: physics
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The categories of this paper are: quant-ph