Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Chemical and kinematical properties of BSSs and HB stars in NGC 6397   We used three sets of high-resolution spectra acquired with the multifiber
facility FLAMES at the Very Large Telescope of the European Southern
Observatory to investigate the chemical and kinematical properties of a sample
of 42 horizontal branch (HB) stars, 18 Blue Straggler Stars (BSSs) and 86 main
sequence turn-off and sub-giant branch stars in the nearby globular cluster NGC
6397. We measured rotational velocities and Fe, O and Mg abundances. All the
unevolved stars in our sample turn out to have low rotational velocites (v sin
i< 10\kms), while HB stars and BSSs show a broad distribution, with values
ranging from 0 to 70 \kms. For HB stars with T<10500 K there is a clear
temperature-oxygen anti-correlation, that can be understood if the star
position along the HB is mainly determined by the He content. The hottest BSSs
and HB stars (with temperatures T>8200 K and T> 10500 K, respectively) also
show significant deviations in their iron abundance with respect to the cluster
metallicity (as traced by the unevolved stars, [Fe/H]=-2.12). While similar
chemical patterns have been already observed in other hot HB stars, this is the
first evidence ever collected for BSSs. We interprete these abundance anomalies
as due to the metal radiative levitation, occurring in stars with shallow or no
convective envelopes.

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The categories of this paper are: alg-geom
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The categories of this paper are: atom-ph
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The categories of this paper are: funct-an
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The categories of this paper are: patt-sol
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The categories of this paper are: math
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The categories of this paper are: gr-qc
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The categories of this paper are: quant-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: stat
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The categories of this paper are: supr-con
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The categories of this paper are: acc-phys
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The categories of this paper are: q-alg
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The categories of this paper are: nlin
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The categories of this paper are: q-bio
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The categories of this paper are: solv-int
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The categories of this paper are: hep-ph