Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Search for Fast X-ray Variability from Active Galactic Nuclei using
  Swift   Blazars are a class of active galactic nuclei (AGNs) known for their very
rapid variabilty in the high energy regions of the electromagnetic spectrum.
Despite this known fast variability, X-ray observations have generally not
revealed variability in blazars with rate doubling or halving timescales less
than approximately 15 min. Since its launch, the Swift X-ray Telescope has
obtained 0.2-10 keV X-ray data on 143 AGNs, including blazars, through intense
target of opportunity observations that can be analyzed in a multiwavelength
context and used to model jet parameters, particularly during flare states. We
have analyzed this broad Swift data set in a search for short timescale
variability in blazars that could limit the size of the emission region in the
blazar jet. While we do find several low-significance possible flares with
potential indications of rapid variability, we find no strong evidence for
rapid ($<$15 minutes) doubling or halving times in flares in the soft X-ray
energy band for the AGNs analyzed.

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The categories of this paper are: chem-ph
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The categories of this paper are: hep-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: mtrl-th
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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: ao-sci
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The categories of this paper are: q-bio
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The categories of this paper are: alg-geom
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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: gr-qc
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The categories of this paper are: physics
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The categories of this paper are: atom-ph
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The categories of this paper are: q-alg
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The categories of this paper are: patt-sol