Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Eccentricity Excitation and Apsidal Resonance Capture in the Planetary
  System Upsilon Andromedae   The orbits of the outer two known planets orbiting Upsilon Andromedae are
remarkably eccentric. Planet C possesses an orbital eccentricity of e1 = 0.253.
For the more distant planet D, e2 = 0.308. Previous dynamical analyses strongly
suggest that the two orbits are nearly co-planar and are trapped in an apsidal
resonance in which the difference between their longitudes of periastron
undergoes a bounded oscillation about 0 degrees. Here we elucidate the origin
of these large eccentricities and of the apsidal alignment. Resonant
interactions between a remnant circumstellar disk of gas lying exterior to the
orbits of both planets can smoothly grow e2. Secular interactions between
planets D and C can siphon off the eccentricity of the former to grow that of
the latter. Externally amplifying e2 during the phase of the apsidal
oscillation when e2/e1 is smallest drives the oscillation amplitude towards
zero. Thus, the substantial eccentricity of planet C and the locking of orbital
apsides are both consequences of externally pumping the eccentricity of planet
D over timescales exceeding apsidal precession periods of order 1e4 yr. We
explain why the recently detected stellar companion to Upsilon Andromedae is
largely dynamically decoupled from the planetary system.

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The categories of this paper are: nucl-ex
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The categories of this paper are: q-fin
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The categories of this paper are: physics
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The categories of this paper are: stat
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-lat
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The categories of this paper are: econ
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The categories of this paper are: nlin
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The categories of this paper are: math-ph
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The categories of this paper are: eess
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The categories of this paper are: hep-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-th
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-th