Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Testing High-latitude Curvature Effect of Gamma-Ray Bursts with {\it
  Fermi} Data: Evidence of Bulk Acceleration in Prompt Emission   When a gamma-ray burst (GRB) emitter stops emission abruptly, the observer
receives rapidly fading emission from high latitudes with respect to the line
of sight, known as the ``curvature effect''. Identifying such emission from GRB
prompt-emission lightcurves would constrain the radius of prompt emission from
the central engine and the composition of GRB jets. We perform a dedicated
search of high-latitude emission (HLE) through spectral and temporal analyses
of a sample of single-pulse bursts detected by the Gamma-ray Burst Monitor on
board the {\it Fermi} satellite. We identify HLE from a subsample of bursts and
constrain the emission radius to be $R_{\rm GRB} \sim (10^{15}-10^{16})$ cm
from the central engine. Some bursts have the HLE decay faster than predicted
by a constant Lorentz factor jet, suggesting that the emission region is
undergoing acceleration during prompt emission. This supports the
Poynting-flux-dominated jet composition for these bursts. The conclusion is
consistent with previous results drawn from spectral-lag modeling of prompt
emission and HLE analysis of X-ray flares.

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The categories of this paper are: gr-qc
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The categories of this paper are: chem-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: stat
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The categories of this paper are: patt-sol
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The categories of this paper are: dg-ga
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The categories of this paper are: math
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The categories of this paper are: acc-phys
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The categories of this paper are: plasm-ph
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The categories of this paper are: funct-an
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The categories of this paper are: hep-lat
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The categories of this paper are: nucl-ex
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The categories of this paper are: adap-org
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The categories of this paper are: bayes-an
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The categories of this paper are: alg-geom
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The categories of this paper are: solv-int