Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A large high-energy gamma-ray flare from the blazar 3C 273   The Compton Gamma-Ray Observatory (CGRO) experiments EGRET and COMPTEL
observed the Virgo sky region continuously for 7 weeks between December 10,
1996 and January 28, 1997. The prominent quasar 3C~273 was found to be the
brightest source in gamma-rays and was significantly detected by EGRET and
COMPTEL. The EGRET experiment observed a time-variable flux at energies above
100 MeV, which reached in a 2-week flaring period (December 30, 1996 to January
14, 1997) its highest flux level observed during the CGRO-era. COMPTEL,
however, does not observe obvious time variability at energies below ~30 MeV
contemporaneous to EGRET. In particular, no flare was observed, indicating that
this outburst is solely a high-energy (>100 MeV) phenomenon. The energy
spectrum between 3 MeV and 10 GeV is well represented by a simple power-law
model. Below 3 MeV a spectral turnover is indicated. Performing spectral
analysis for different time periods, we found evidence for a spectral hardening
during the flaring period, which is consistent with the flare occurring mainly
at the higher energies and with its absence at COMPTEL energies of a few MeV.
This may be interpreted as an indication that the emission in the EGRET energy
range is dominated by a different radiation mechanism than the MeV emission. We
argue that the most likely mechanism for the high-energy flare is
inverse-Compton scattering of reprocessed accretion-disk radiation.

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The categories of this paper are: q-fin
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The categories of this paper are: stat
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The categories of this paper are: hep-ex
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The categories of this paper are: eess
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The categories of this paper are: chem-ph
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The categories of this paper are: math
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The categories of this paper are: adap-org
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The categories of this paper are: acc-phys
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The categories of this paper are: bayes-an
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The categories of this paper are: cs
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The categories of this paper are: cond-mat
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The categories of this paper are: math-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-lat
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The categories of this paper are: ao-sci