Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Na-O anticorrelation in horizontal branch stars. IV. M22   We obtained high-resolution spectra for 94 candidate stars belonging to the
HB of M22 with FLAMES. The HB stars we observed span a restricted temperature
range (7,800<Teff<11,000 K), where about 60% of the HB stars of M22 are. Within
our sample, we can distinguish three groups of stars segregated (though
contiguous) in colours: Group 1 (49 stars) is metal-poor, N-normal, Na-poor and
O-rich with abundances that match those determined for the primordial group of
RGB stars from previous studies. Group 2 (23 stars) is still metal-poor, but it
is N- and Na-rich, though only very mildly depleted in O. We can identify this
intermediate group as the progeny of the metal-poor RGB stars that occupy an
intermediate location along the Na-O anti-correlation. The third group (20
stars) is metal-rich, Na-rich, and O-rich and likely corresponds to the most
O-rich component of the previously found metal-rich RGB population. We did not
observe any severely O-depleted stars and we think that the progeny of these
stars falls on the hotter part of the HB. The metal-rich population is also
over-abundant in Sr, in agreement with results for corresponding RGB and SGB
stars. However, we do not find any significant variation in the ratio between
the sum of N and O abundances to Fe. There is some evidence of an enhancement
of He content for Groups 2 and 3 stars (Y=0.338\pm 0.014\pm 0.05). Our results
agree with the proposition that chemical composition drives the location of
stars along the HB of a GC. Furthermore, we found a number of fast rotators.
They are concentrated in a restricted temperature range along the HB of M22.

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The categories of this paper are: funct-an
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The categories of this paper are: hep-th
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The categories of this paper are: hep-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-alg
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The categories of this paper are: nucl-th
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The categories of this paper are: cond-mat
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The categories of this paper are: q-fin
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The categories of this paper are: atom-ph
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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: acc-phys
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The categories of this paper are: alg-geom
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The categories of this paper are: cs
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The categories of this paper are: stat
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The categories of this paper are: nlin