Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Swift monitoring of NGC 5548: X-ray reprocessing and short term
  UV/optical variability   Lags measured from correlated X-ray/UV/optical monitoring of AGN allow us to
determine whether UV/optical variability is driven by reprocessing of X-rays or
X-ray variability is driven by UV/optical seed photon variations. We present
the results of the largest study to date of the relationship between the X-ray,
UV and optical variability in an AGN with 554 observations, over a 750d period,
of the Seyfert 1 galaxy NGC 5548 with Swift. There is a good overall
correlation between the X-ray and UV/optical bands, particularly on short
timescales (tens of days). These bands lag the X-ray band with lags which are
proportional to wavelength to the power 1.23+/-0.31. This power is very close
to the power (4/3) expected if short timescale UV/optical variability is driven
by reprocessing of X-rays by a surrounding accretion disc.
  The observed lags, however, are longer than expected from a standard
Shakura-Sunyaev accretion disc with X-ray heating, given the currently accepted
black hole mass and accretion rate values, but can be explained with a slightly
larger mass and accretion rate, and a generally hotter disc.
  Some long term UV/optical variations are not paralleled exactly in the
X-rays, suggesting an additional component to the UV/optical variability
arising perhaps from accretion rate perturbations propagating inwards through
the disc.

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The categories of this paper are: eess
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The categories of this paper are: patt-sol
8
The categories of this paper are: hep-ex
0
The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph
4
The categories of this paper are: cond-mat
30
The categories of this paper are: q-alg
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The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
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The categories of this paper are: cmp-lg
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The categories of this paper are: bayes-an
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The categories of this paper are: q-fin
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The categories of this paper are: comp-gas
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The categories of this paper are: solv-int
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The categories of this paper are: nlin
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The categories of this paper are: mtrl-th