Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Discovery of a Metal-poor, Luminous Post-AGB Star that Failed the Third
  Dredge-up   Post-asymptotic giant branch (post-AGB) stars are known to be chemically
diverse. In this paper we present the first observational evidence of a star
that has failed the third dredge-up (TDU). J005252.87-722842.9 is a A-type
($T_{\rm eff}$ = 8250 $\pm$ 250K) luminous (8200 $\pm$ 700 $\rm L_{\odot}$),
metal-poor ($\textrm{[Fe/H]}$ = $- 1.18 \pm$ 0.10), low-mass (M$_{\rm initial}$
$\approx$ 1.5 $-$ 2.0 $\rm M_{\odot}$) post-AGB star in the Small Magellanic
Cloud. Through a systematic abundance study, using high-resolution optical
spectra from UVES, we found that this likely post-AGB object shows an
intriguing photospheric composition with no confirmed carbon-enhancement (upper
limit of [C/Fe] $<$ 0.50) nor enrichment of $s$-process elements. We derived an
oxygen abundance of [O/Fe] = 0.29 $\pm$ 0.1. For Fe and O, we took into account
the effects of non-local thermodynamic equilibrium (NLTE). We could not derive
an upper limit for the nitrogen abundance as there are no useful nitrogen lines
within our spectral coverage. The chemical pattern displayed by this object has
not been observed in single or binary post-AGBs. Based on its derived stellar
parameters and inferred evolutionary state, single star nucleosynthesis models
predict that this star should have undergone TDU episodes while on the AGB and
be carbon-enriched. However, our observations are in contrast with these
predictions. We identify two possible Galactic analogues which are likely to be
post-AGB stars, but the lack of accurate distances (hence luminosities) to
these objects does not allow us to confirm their post-AGB status. If they have
low luminosities then they are likely to be dusty post-RGB stars. The discovery
of J005252.87-722842.9 reveals a new stellar evolutionary channel whereby a
star evolves without any third dredge-up episodes.

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The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
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The categories of this paper are: hep-th
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The categories of this paper are: math
5
The categories of this paper are: gr-qc
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The categories of this paper are: patt-sol
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The categories of this paper are: comp-gas
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-lat
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The categories of this paper are: cmp-lg
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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: stat
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The categories of this paper are: hep-ex
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The categories of this paper are: nucl-th
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The categories of this paper are: ao-sci