Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Large-Scale Survey of Neutron-Capture Element Abundances in Planetary
  Nebulae   We present results from the first large-scale survey of neutron(n)-capture
element abundances in planetary nebulae (PNe). This survey was motivated by the
fact that a PN may be enriched in n-capture elements if its progenitor star
experienced s-process nucleosynthesis during the asymptotic giant branch (AGB)
phase. [Kr III] 2.199 and/or [Se IV] 2.287 $\mu$m were detected in 81 PNe out
of 120 PNe, for a detection rate of nearly 70%. We derive Se and Kr abundances
or upper limits using ionization correction factors derived from
photoionization models. A significant range is found in the Se and Kr
abundances, from near solar (no enrichment), to enriched by a factor of ten.
Our survey has increased the number of PNe with known n-capture element
abundances by an order of magnitude, enabling us to explore correlations
between s-process enrichments and other nebular and central star properties. In
particular, the Se and Kr enrichments display a positive correlation with
nebular C/O ratios, as theoretically expected. Peimbert Type I PNe and bipolar
PNe, whose progenitors are believed to be intermediate-mass stars (>3-4 M_sun),
exhibit little or no s-process enrichment. Interestingly, PNe with H-deficient
[WC] central stars do not exhibit systematically larger s-process enrichments
than other PNe, despite the fact that their central stars are enriched in C and
probably n-capture elements. Finally, the few PNe in our sample with known or
probable binary central star systems exhibit little s-process enrichment, which
may be explained if binary interactions truncated their AGB phases. We also
briefly discuss a new observational program to detect optical emission lines of
n-capture elements, and new atomic data calculations that will greatly improve
the accuracy of n-capture element abundance determinations in PNe.

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The categories of this paper are: math
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The categories of this paper are: cmp-lg
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The categories of this paper are: nlin
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The categories of this paper are: hep-ph
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The categories of this paper are: supr-con
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The categories of this paper are: math-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-th
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The categories of this paper are: econ
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The categories of this paper are: stat
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The categories of this paper are: cs
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-fin
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The categories of this paper are: patt-sol
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The categories of this paper are: comp-gas