Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Stellar Abundance Observations   Ground- and space-based observations of stellar heavy element abundances are
providing a clearer picture of the chemical evolution of the Galaxy. A large
number of (r)apid and (s)low neutron capture process elements, including the
first Hubble Space Telescope observations of Pt, Os, Pb and Ge, have been
identified in metal-poor, galactic halo stars. In the very low metallicity
(i.e. [Fe/H] $<$ --2.0) stars, the abundance pattern of the elements from Ba
through the third neutron-capture peak (Os-Pt) is consistent with a scaled
solar {\it r}-process distribution. These results support previous observations
that demonstrate the operation of the {\it r}-process, including the synthesis
of the heaviest such elements, early in the history of the Galaxy. New
ground-based observations further confirm that the {\it s}-process element Ba
and the {\it r}-process element Eu were both synthesized solely by the
r-process at low metallicities, and indicate the onset of the {\it s}-process
occurred near [Fe/H] = --2. Over a range of metallicity (--2.90 $<$ [Fe/H] $<$
--0.86) the data indicate that there exist real star-to-star differences in the
ratios of the [n-capture/Fe] abundances as well as in the actual spectra of the
stars.

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The categories of this paper are: chem-ph
9
The categories of this paper are: nlin
13
The categories of this paper are: quant-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: mtrl-th
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The categories of this paper are: eess
0
The categories of this paper are: hep-ph
2
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: hep-lat
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The categories of this paper are: q-fin
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The categories of this paper are: hep-th
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The categories of this paper are: solv-int
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph