Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The flux-dependent rms variability of X-ray binaries in the optical   A linear relation between absolute rms variability and flux in X-ray
observations of compact accreting sources has recently been identified. Such a
relation suggests that X-ray lightcurves are non-linear and composed of a
lognormal distribution of fluxes. Here, a first investigation of the optical
rms vs. flux behavior in X-ray binaries is presented. Fast timing data on three
binaries in the X-ray low/hard state are examined. These are XTE J1118+480, GX
339-4 and SWIFT J1753.5-0127 -- all show aperiodic (non-reprocessed) optical
fluctuation components. Optical rms amplitude is found to increase with flux in
all sources. A linear fit results in a positive offset along the flux axis, for
most frequency ranges investigated. The X-ray and optical relation slopes track
the source fractional variability amplitudes. This is especially clear in the
case of GX 339-4, which has the largest optical variance of the three targets.
Non-linearity is supported in all cases by the fact that flux distributions of
the optical lightcurves are better described with a lognormal function than a
simple gaussian. Significant scatter around linearity is found in the relation
for the two sources with lower optical variability amplitude, though
observational biases may well contribute to this. Implications for accretion
models are discussed, and the need for long well-sampled optical lightcurves is
emphasized.

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The categories of this paper are: hep-ph
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The categories of this paper are: nlin
24
The categories of this paper are: dg-ga
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The categories of this paper are: eess
28
The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
30
The categories of this paper are: q-alg
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The categories of this paper are: adap-org
20
The categories of this paper are: acc-phys
36
The categories of this paper are: cmp-lg
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The categories of this paper are: math-ph
37
The categories of this paper are: supr-con
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The categories of this paper are: funct-an
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The categories of this paper are: hep-th
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The categories of this paper are: solv-int
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The categories of this paper are: stat