Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: First Constraints on Rings in the Pluto System   Simple theoretical calculations have suggested that small body impacts onto
Pluto's newly discovered small satellites, Nix and Hydra, are capable of
generating time-variable rings or dust sheets in the Pluto system. Using
HST/ACS data obtained on 2006 February 15 and 2006 March 2, we find no
observational evidence for such a ring system and present the first constraints
on the present-day I/F and optical depth of a putative ring system. At the
1500-km radial resolution of our search, we place a 3-sigma upper limit on the
azimuthally-averaged normal I/F of ring particles of 5.1x10^-7 at a distance of
42,000 km from the Pluto-Charon barycenter, the minimum distance for a
dynamically stable ring (Stern et al., 1994; Nagy et al., 2006); 4.4x10^-7 at
the orbit of Nix; and 2.5x10^-7 at the orbit of Hydra. For an assumed ring
particle albedo of 0.04 (0.38), these I/F limits translate into 3-sigma upper
limits on the normal optical depth of macroscopic ring particles of 1.3x10^-5
(1.4x10^-6), 1.1x10^-5 (1.2x10^-6), 6.4x10^-6 (6.7x10^-7), respectively. Were
the New Horizons spacecraft to fly through a ring system with optical depth of
1.3x10^-5, it would collide with a significant number of potentially damaging
ring particles. We therefore recommend that unless tighter constraints can be
obtained, New Horizons cross the putative ring plane within 42,000 km of the
Pluto-Charon barycenter, where rings are dynamically unstable. We derive a
crude estimate of the lifetime of putative ring paritcles of 900 years.

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The categories of this paper are: adap-org
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The categories of this paper are: nucl-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: hep-ex
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The categories of this paper are: nucl-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: quant-ph
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The categories of this paper are: solv-int
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The categories of this paper are: alg-geom
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The categories of this paper are: stat
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The categories of this paper are: q-alg
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The categories of this paper are: chem-ph
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The categories of this paper are: math-ph
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The categories of this paper are: funct-an
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The categories of this paper are: math