Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Diffusive Cosmic-ray Acceleration in Sagittarius A*   Together, the Fermi-LAT and HESS have revealed the presence of an unusual
GeV-TeV source coincident with Sgr A* at the Galactic center. Its high-energy
emission appears to be bimodal, hinting at an energizing process more
sophisticated than mere shock acceleration. It has been suggested that this may
be evidence of strong, rapid variability, as required if Sgr A*'s emission were
responsible for the fluorescent X-ray echos detected in nearby molecular
clouds. In this {\it Letter}, however, we show that stochastic acceleration in
a more realistic two-phase environment surrounding the central black hole can
accommodate Sgr A*'s high-energy spectrum quite well. We therefore suggest that
the Fermi-HESS data alone do not necessarily provide evidence for strong
variability in Sgr A*.

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The categories of this paper are: patt-sol
20
The categories of this paper are: acc-phys
1
The categories of this paper are: cs
13
The categories of this paper are: quant-ph
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The categories of this paper are: adap-org
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The categories of this paper are: chem-ph
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The categories of this paper are: q-alg
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The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
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The categories of this paper are: cmp-lg
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The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
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The categories of this paper are: mtrl-th
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The categories of this paper are: eess
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The categories of this paper are: comp-gas
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The categories of this paper are: atom-ph