Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Molecular Line Survey of the Highly Evolved Carbon Star CIT 6   We present a spectral line survey of the C-rich envelope CIT 6 in the 2mm and
1.3mm bands carried out with the Arizona Radio Observatory (ARO) 12m telescope
and the Heinrich Hertz Submillimeter Telescope (SMT). The observations cover
the frequency ranges of 131--160 GHz, 219--244 GHz, and 252--268 GHz with
typical sensitivity limit of T_R<10 mK. A total of 74 individual emission
features are detected, of which 69 are identified to arise from 21 molecular
species and isotopologues, with 5 faint lines remaining unidentified. Two new
molecules (C4H and CH3CN) and seven new isotopologues (C17O, 29SiC2, 29SiO,
30SiO, 13CS, C33S, and CS) are detected in this object for the first time. The
column densities, excitation temperatures, and fractional abundances of the
detected molecules are determined using rotation diagram analysis. Comparison
of the spectra of CIT 6 to that of IRC+10216 suggests that the spectral
properties of CIT 6 are generally consistent with those of IRC+10216. For most
of the molecular species, the intensity ratios of the lines detected in the two
objects are in good agreement with each other. Nevertheless, there is evidence
suggesting enhanced emission from CN and HC3N and depleted emission from HCN,
SiS, and C4H in CIT 6. Based on their far-IR spectra, we find that CIT 6
probably has a lower dust-to-molecular gas ratio than IRC+10216. To investigate
the chemical evolution of evolved stars, we compare the molecular abundances in
the AGB envelopes CIT 6 and IRC+10216 and those in the bright proto-planetary
nebula CRL 618. The implication on the circumstellar chemistry is discussed.

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The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
16
The categories of this paper are: stat
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The categories of this paper are: bayes-an
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The categories of this paper are: eess
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The categories of this paper are: patt-sol
1
The categories of this paper are: cs
0
The categories of this paper are: hep-ph
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The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
4
The categories of this paper are: cond-mat
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The categories of this paper are: acc-phys
2
The categories of this paper are: math
11
The categories of this paper are: hep-lat
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The categories of this paper are: nlin