Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Cometary activity at 25.7 AU: Hale--Bopp 11 years after perihelion   Eleven years after its perihelion, comet C/1995 O1 (Hale-Bopp) is still
active. Between October 20--22, 2007, we detected a diffuse coma of 180x10^3$km
in diameter with a slight elongation toward N/S direction. The integrated
brightness was 20.04 mag in R_C, implying Af\rho=300 m and albedo x dust
surface $a_RC$=4300 km^2. The coma was relatively red at V-R=0.66 mag, which is
consistent with that of the dust in other comets. The observed properties and
the overall fading in brightness between 10 AU and 26 AU follow the predicted
behaviour of CO-driven activity (Capria et al. 2002). This is the most distant
cometary activity ever observed.

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The categories of this paper are: mtrl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-fin
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The categories of this paper are: adap-org
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The categories of this paper are: quant-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: comp-gas
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The categories of this paper are: funct-an
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The categories of this paper are: chao-dyn
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The categories of this paper are: atom-ph
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The categories of this paper are: cs
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The categories of this paper are: econ
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The categories of this paper are: dg-ga
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The categories of this paper are: q-bio
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The categories of this paper are: hep-th