Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Four-hundred Very Metal-Poor Stars Studied with LAMOST and Subaru. II.
  Elemental abundances   We present homogeneous abundance analysis of over 20 elements for 385 very
metal-poor (VMP) stars based on the LAMOST survey and follow-up observations
with the Subaru Telescope. It is the largest high-resolution VMP sample
(including 363 new objects) studied by a single program, and the first attempt
to accurately determine evolutionary stages for such a large sample based on
Gaia parallaxes. The sample covers a wide metallicity range from [Fe/H]=-1.7
down to [Fe/H]=-4.3, including over 110 objects with [Fe/H]<-3.0. The expanded
coverage in evolutionary status makes it possible to define abundance trends
respectively for giants and turn-off stars. The newly obtained abundance data
confirm most abundance trends found by previous studies, but also provide
useful update and new sample of outliers. The Li plateau is seen in -2.5 <
[Fe/H] <-1.7 in our sample, whereas the average Li abundance is clearly lower
at lower metallicity. Mg, Si, and Ca are overabundant with respect to Fe,
showing decreasing trend with increasing metallicity. Comparisons with chemical
evolution models indicate that the over-abundance of Ti, Sc, and Co are not
well reproduced by current theoretical predictions. Correlations are seen
between Sc and alpha-elements, while Zn shows a detectable correlation only
with Ti but not with other alpha-elements. The fraction of carbon-enhanced
stars ([C/Fe]> 0.7) is in the range of 20-30% for turn-off stars depending on
the treatment of objects for which C abundance is not determined, which is much
higher than that in giants (~8%). Twelve Mg-poor stars ([Mg/Fe] < 0.0) have
been identified in a wide metallicity range from [Fe/H] =-3.8 through -1.7.
Twelve Eu-rich stars ([Eu/Fe]> 1.0) have been discovered in -3.4 <[Fe/H]< -2.0,
enlarging the sample of r-process-enhanced stars with relatively high
metallicity.

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The categories of this paper are: funct-an
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The categories of this paper are: bayes-an
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The categories of this paper are: solv-int
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The categories of this paper are: atom-ph
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The categories of this paper are: q-alg
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The categories of this paper are: dg-ga
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The categories of this paper are: cs
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The categories of this paper are: hep-ex
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The categories of this paper are: alg-geom
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The categories of this paper are: econ
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The categories of this paper are: adap-org
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The categories of this paper are: math
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The categories of this paper are: nucl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: eess
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The categories of this paper are: quant-ph