Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Transit infrared spectroscopy of the hot neptune around GJ 436 with the
  Hubble Space Telescope   The nearby transiting system GJ 436b offers a unique opportunity to probe the
structure and atmosphere of an extra-solar "hot Neptune". In this Letter, we
present the main results of observations covering two transit events with the
NICMOS camera on the Hubble Space Telescope. The data consist in high-cadence
time series of grism spectra covering the 1.1-1.9 micron spectral range. We
find Rpl=4.04 +- 0.10 R_earth and Rstar= 0.446 +- 0.011 Rsun for the planet and
star radius, confirming and improving earlier measurements with ground-based
photometry and a Spitzer lightcurve at 8 microns, as opposed to a much higher
value obtained with the Fine Guidance Sensor on the Hubble Space Telescope. We
measure no departure from strict periodicity in the transits to the level of ~7
seconds. This strongly disfavours the proposed explanation of the orbital
eccentricity of GJ 436b in terms of the perturbation by another close-by
planet. We measure a flat transmission spectrum at the level of a few parts per
10 000 in flux, with no significant signal in the 1.4-micron water band to a
level comparable to the maximum amplitude of the effect predicted by planetary
atmosphere models.

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The categories of this paper are: q-alg
15
The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio
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The categories of this paper are: supr-con
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The categories of this paper are: cmp-lg
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The categories of this paper are: acc-phys
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The categories of this paper are: q-fin
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The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
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The categories of this paper are: eess
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The categories of this paper are: chem-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: math
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The categories of this paper are: quant-ph
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The categories of this paper are: mtrl-th
25
The categories of this paper are: patt-sol