Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The R-Process Alliance: 2MASS J09544277+5246414, the Most
  Actinide-Enhanced R-II Star Known   We report the discovery of a new actinide-boost star, 2MASS
J09544277+5246414, originally identified as a very bright (V = 10.1), extremely
metal-poor ([Fe/H] = -2.99) K giant in the LAMOST survey, and found to be
highly r-process-enhanced (r-II; [Eu/Fe]= +1.28]), during the snapshot phase of
the R-Process Alliance (RPA). Based on a high S/N, high-resolution spectrum
obtained with the Harlan J. Smith 2.7-m telescope, this star is the first
confirmed actinide-boost star found by RPA efforts. With an enhancement of
[Th/Eu] = +0.37, 2MASS J09544277+5246414 is also the most actinide-enhanced
r-II star yet discovered, and only the sixth metal-poor star with a measured
uranium abundance ([U/Fe] = +1.40). Using the Th/U chronometer, we estimate an
age of 13.0+/-4.7 Gyr for this star. The unambiguous actinide-boost signature
of this extremely metal-poor star, combined with additional r-process-enhanced
and actinide-boost stars identified by the RPA, will provide strong constraints
on the nature and origin of the r-process at early times.

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The categories of this paper are: physics
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The categories of this paper are: hep-ex
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The categories of this paper are: supr-con
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The categories of this paper are: chao-dyn
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The categories of this paper are: nlin
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The categories of this paper are: nucl-ex
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The categories of this paper are: gr-qc
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-th
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The categories of this paper are: q-bio
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The categories of this paper are: hep-ph
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The categories of this paper are: hep-th
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The categories of this paper are: funct-an
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The categories of this paper are: math
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg