Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Rayleigh scattering in the transit spectrum of HD 189733b   The transit spectrum of the exoplanet HD 189733b has recently been obtained
between 0.55 and 1.05 microns. Here we present an analysis of this spectrum. We
develop first-order equations to interpret absorption spectra. In the case of
HD 189733b, we show that the observed slope of the absorption as a function of
wavelength is characteristic of extinction proportional to the inverse of the
fourth power of the wavelength (lambda^-4). Assuming an extinction dominated by
Rayleigh scattering, we derive an atmospheric temperature of 1340+/-150 K. If
molecular hydrogen is responsible for the Rayleigh scattering, the atmospheric
pressure at the planetary characteristic radius of 0.1564 stellar radius must
be 410+/-30 mbar. However the preferred scenario is scattering by condensate
particles. Using the Mie approximation, we find that the particles must have a
low value for the imaginary part of the refraction index. We identify MgSiO3 as
a possible abundant condensate whose particle size must be between 0.01 and 0.1
microns. For this condensate, assuming solar abundance, the pressure at 0.1564
stellar radius is found to be between a few microbars and few millibars, and
the temperature is found to be in the range 1340-1540 K, and both depend on the
particle size.

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The categories of this paper are: solv-int
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The categories of this paper are: comp-gas
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The categories of this paper are: supr-con
9
The categories of this paper are: nlin
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The categories of this paper are: eess
8
The categories of this paper are: hep-ex
26
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: math-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: econ
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The categories of this paper are: quant-ph
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The categories of this paper are: adap-org
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The categories of this paper are: chao-dyn
0
The categories of this paper are: hep-ph
3
The categories of this paper are: physics