Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Highly He-Rich Matter Dredged Up by Extra Mixing through Stellar
  Encounters in Globular Clusters   The unveiled main-sequence splitting in omega Centauri as well as NGC 2808
suggests that matter highly-enriched in He (in terms of its mass fraction
Y~0.4) was produced and made the color of some main-sequence stars bluer in
these globular clusters (GCs). The potential production site for the He-rich
matter is generally considered to be massive AGB stars that experience the
second dredge-up. However, it is found that massive AGB stars provide the
matter with Y~0.35 at most, while the observed blue-shift requires the presence
of Y~0.4 matter. Here, we show that extra mixing, which operates in the red
giant phase of stars less massive than ~2Msun, could be a mechanism that
enhances He content in their envelopes up to Y~0.4. The extra mixing is
supposed to be induced by red giant encounters with other stars in a
collisional system like GCs. The Y~0.4 matter released in the AGB phase has
alternative fates to (i) escape from a GC or (ii) be captured by kinematically
cool stars through encounters. The AGB ejecta in omega Cen, which follows the
latter case, can supply sufficient He to cause the observed blue-shift.
Simultaneously, this scheme generates the extreme horizontal branch, as
observed in omega Cen in response to the higher mass loss rates, which is also
caused by stellar encounters.

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The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
32
The categories of this paper are: atom-ph
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The categories of this paper are: math-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: quant-ph
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The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
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The categories of this paper are: nucl-ex
2
The categories of this paper are: math
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The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc
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The categories of this paper are: nlin
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-th