Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Extrasolar Binary Planets I: Formation by tidal capture during
  planet-planet scattering   We have investigated i) the formation of gravitationally bounded pairs of
gas-giant planets (which we call "binary planets") from capturing each other
through planet-planet dynamical tide during their close encounters and ii) the
following long-term orbital evolution due to planet-planet and planet-star {\it
quasi-static} tides. For the initial evolution in phase i), we carried out
N-body simulations of the systems consisting of three jupiter-mass planets
taking into account the dynamical tide. The formation rate of the binary
planets is as much as 10% of the systems that undergo orbital crossing and this
fraction is almost independent of the initial stellarcentric semi-major axes of
the planets, while ejection and merging rates sensitively depend on the
semi-major axes. As a result of circularization by the planet-planet dynamical
tide, typical binary separations are a few times the sum of the physical radii
of the planets. After the orbital circularization, the evolution of the binary
system is governed by long-term quasi-static tide. We analytically calculated
the quasi-static tidal evolution in later phase ii). The binary planets first
enter the spin-orbit synchronous state by the planet-planet tide. The
planet-star tide removes angular momentum of the binary motion, eventually
resulting in a collision between the planets. However, we found that the binary
planets survive the tidal decay for main-sequence life time of solar-type stars
(~10Gyrs), if the binary planets are beyond ~0.3 AU from the central stars.
These results suggest that the binary planets can be detected by transit
observations at >0.3AU.

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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: mtrl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: stat
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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: eess
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-th