Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: When Do Internal Shocks End and External Shocks Begin? Early-Time
  Broadband Modelling of GRB 051111   Even with the renaissance in gamma-ray burst (GRB) research fostered by the
Swift satellite, few bursts have both contemporaneous observations at long
wavelengths and exquisite observations at later times across the
electromagnetic spectrum. We present here contemporaneous imaging with the KAIT
robotic optical telescope, dense optical sampling with Lulin, and supplemented
with infrared data from PAIRITEL and radio to gamma-ray data from the
literature. For the first time, we can test the constancy of microphysical
parameters in the internal-external shock paradigm and carefully trace the flow
of energy from the GRB to the surrounding medium. KAIT data taken <~1 minute
after the start of GRB051111 and coinciding with the fading gamma-ray tail of
the prompt emission indicate a smooth re-injection of energy into the shock. No
color change is apparent in observations beginning ~1.5 minutes after the GRB
and lasting for the first hour after the burst. There are achromatic flux
modulations about the best-fit model at late (t~10^4 s) times, possibly due to
variations in the external density. We find that the host-galaxy extinction is
well fit by a curve similar to that ofthe Small Magellanic Cloud. Low visual
extinction, A_V~0.2 mag, combined with high column densities determined from
the X-ray and optical spectroscopy (N_H> 10^21 cm^-2), indicate a low
dust-to-metals ratio and a possible over-abundance of the light metals. An
apparent small ratio of total to selective extinction (R_V~2) argues against
dust destruction by the GRB. Time constancy of both the IR/optical/UV spectral
energy distribution and the soft X-ray absorption suggests that the absorbing
material is not local to the GRB.

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The categories of this paper are: quant-ph
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The categories of this paper are: eess
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The categories of this paper are: gr-qc
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The categories of this paper are: math
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The categories of this paper are: nucl-th
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The categories of this paper are: q-bio
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The categories of this paper are: hep-ex
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The categories of this paper are: cs
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The categories of this paper are: chem-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: bayes-an
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The categories of this paper are: math-ph
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The categories of this paper are: physics
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The categories of this paper are: nlin
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The categories of this paper are: atom-ph
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The categories of this paper are: q-fin