Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: NGC 6778: Strengthening the link between extreme abundance discrepancy
  factors and central star binarity in planetary nebulae   We present new optical spectra of the nearby, bright, planetary nebula NGC
6778. The nebula has been known to emit strong recombination lines for more
than 40 years but this is the first detailed study of its abundances. Heavy
element abundances derived from recombination lines are found to exceed those
from collisionally excited lines by a factor of ~20 in an integrated spectrum
of the nebula, which is among the largest known abundance discrepancy factors.
Spatial analysis of the spectra shows that the abundance discrepancy factor is
strongly, centrally peaked, reaching ~40 close to the central star. The central
star of NGC 6778 is known to be a short period binary, further strengthening
the link between high nebular abundance discrepancy factors and central star
binarity.

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The categories of this paper are: gr-qc
32
The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
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The categories of this paper are: q-fin
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The categories of this paper are: chem-ph
9
The categories of this paper are: nlin
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The categories of this paper are: solv-int
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The categories of this paper are: hep-lat
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The categories of this paper are: quant-ph
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The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
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The categories of this paper are: hep-ex
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The categories of this paper are: plasm-ph
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The categories of this paper are: stat
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The categories of this paper are: cs
25
The categories of this paper are: patt-sol