Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Search for TeV Gamma-ray Emission from GRB 100621A, an extremely bright
  GRB in X-rays, with H.E.S.S   The long gamma-ray burst (GRB) 100621A, at the time the brightest X-ray
transient ever detected by Swift-XRT in the $0.3\textrm{--}10$ keV range, has
been observed with the H.E.S.S. imaging air Cherenkov telescope array,
sensitive to gamma radiation in the very-high-energy (VHE, $>100$ GeV) regime.
Due to its relatively small redshift of $z\sim0.5$, the favourable position in
the southern sky and the relatively short follow-up time ($<700 \rm{s}$ after
the satellite trigger) of the H.E.S.S. observations, this GRB could be within
the sensitivity reach of the H.E.S.S. instrument. The analysis of the H.E.S.S.
data shows no indication of emission and yields an integral flux upper limit
above $\sim$380 GeV of $4.2\times10^{-12} \rm cm^{-2}s^{-1}$ (95 % confidence
level), assuming a simple Band function extension model. A comparison to a
spectral-temporal model, normalised to the prompt flux at sub-MeV energies,
constraints the existence of a temporally extended and strong additional hard
power law, as has been observed in the other bright X-ray GRB 130427A. A
comparison between the H.E.S.S. upper limit and the contemporaneous energy
output in X-rays constrains the ratio between the X-ray and VHE gamma-ray
fluxes to be greater than 0.4. This value is an important quantity for
modelling the afterglow and can constrain leptonic emission scenarios, where
leptons are responsible for the X-ray emission and might produce VHE gamma
rays.

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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-lat
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The categories of this paper are: gr-qc
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The categories of this paper are: funct-an
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The categories of this paper are: comp-gas
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The categories of this paper are: alg-geom
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The categories of this paper are: solv-int
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The categories of this paper are: hep-th
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The categories of this paper are: q-alg
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The categories of this paper are: q-fin
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The categories of this paper are: q-bio
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The categories of this paper are: adap-org
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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-ph
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The categories of this paper are: eess