Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: J0023+0307: A mega metal-poor dwarf star from SDSS/BOSS   Only a handful of stars have been identified with an iron abundance
[Fe/H]<-5, and only one at [Fe/H]<-7. These stars have very large
carbon-to-iron ratios, with A(C)~7.0, most likely due to fallback in
core-collapse supernovae, which makes their total metallicity Z much higher
than their iron abundances. The failure to find population III stars, those
with no metals, has been interpreted, with support from theoretical modeling,
as the result of a top-heavy initial mass function. With zero or very low metal
abundance limiting radiative cooling, the formation of low-mass stars could be
inhibited. Currently, the star SDSS J1029+1729 sets the potential metallicity
threshold for the formation of low-mass stars at log Z/Z_0~-5. We have
identified SDSS J0023+0307, a primitive star with T_eff =6188+-84 K, and log
g=4.9+-0.5, an upper limit [Fe/H]< -6.6, and a carbon abundance A(C)< 6.3. In
our quest to push down the metallicity threshold we find J0023+0307 to be one
of the two most iron-poor stars known, and it exhibits less carbon that most of
stars at [Fe/H]< -5.

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The categories of this paper are: dg-ga
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The categories of this paper are: ao-sci
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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: plasm-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-lat
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The categories of this paper are: adap-org
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph
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The categories of this paper are: econ
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The categories of this paper are: patt-sol
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The categories of this paper are: solv-int
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The categories of this paper are: gr-qc
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The categories of this paper are: chem-ph
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The categories of this paper are: eess