Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fermi-LAT Observations of the Gamma-ray Burst GRB 130427A   The observations of the exceptionally bright gamma-ray burst (GRB) 130427A by
the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope provide
constraints on the nature of such unique astrophysical sources. GRB 130427A had
the largest fluence, highest-energy photon (95 GeV), longest $\gamma$-ray
duration (20 hours), and one of the largest isotropic energy releases ever
observed from a GRB. Temporal and spectral analyses of GRB 130427A challenge
the widely accepted model that the non-thermal high-energy emission in the
afterglow phase of GRBs is synchrotron emission radiated by electrons
accelerated at an external shock.

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The categories of this paper are: cs
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The categories of this paper are: plasm-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: cond-mat
31
The categories of this paper are: ao-sci
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The categories of this paper are: econ
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The categories of this paper are: mtrl-th
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The categories of this paper are: solv-int
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The categories of this paper are: stat
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The categories of this paper are: hep-lat
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The categories of this paper are: q-bio
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The categories of this paper are: hep-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: q-fin
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The categories of this paper are: alg-geom
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The categories of this paper are: supr-con