Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Discovery of very high-energy gamma-ray emission from the LBL object BL
  Lacertae   The low-frequency peaked BL Lac (LBL) object BL Lacertae was observed with
the MAGIC telescope from 2005 August to December (22.2 hr), and from 2006 July
to September (26.0 hr). A very high energy (VHE) gamma-ray signal was
discovered with a 5.1 sigma excess in the 2005 data. Above 200 GeV, an integral
flux of (0.6+-0.2)x10e-11 m-2 s-1 was measured, corresponding to approximately
3% of the Crab flux. The differential spectrum between 150 and 900 GeV is
rather steep, with a photon index of -3.6+-0.5. The light curve shows no
significant variability during the observations in 2005. For the first time a
clear detection of VHE gamma-ray emission from an LBL object was obtained. The
2006 data show no significant excess. This drop in flux follows the observed
trend in optical activity

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The categories of this paper are: bayes-an
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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: comp-gas
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The categories of this paper are: solv-int
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The categories of this paper are: hep-lat
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-bio
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The categories of this paper are: ao-sci
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The categories of this paper are: eess
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-th
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The categories of this paper are: quant-ph
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The categories of this paper are: math-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: patt-sol