Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Eccentricity Evolution in Gaseous Dynamical Friction   We analyse how drag forces modify the orbits of objects moving through
extended gaseous distributions. We consider how hydrodynamic (surface area)
drag forces and dynamical friction (gravitational) drag forces drive the
evolution of orbital eccentricity. While hydrodynamic drag forces cause
eccentric orbits to become more circular, dynamical friction drag can cause
orbits to become more eccentric. We develop a semi-analytic model that
accurately predicts these changes by comparing the total work and torque
applied to the orbit at periapse and apoapse. We use a toy model of a radial
power-law density profile, $\rho \propto r^{-\gamma}$, to determine that there
is a critical $\gamma = 3$ power index which separates the eccentricity
evolution: orbits become more eccentric for $\gamma < 3$ and circularize for
$\gamma > 3$. We apply these findings to the infall of a Jupiter-like planet
into the envelope of its host star. The hydrostatic envelopes of stars are
defined by steep density gradients near the limb and shallower gradients in the
interior. Under the influence of gaseous dynamical friction, an infalling
object's orbit will first decrease in eccentricity, then increase. The critical
separation that delineates these regimes is predicted by the local density
slope and is linearly dependent on polytropic index. More broadly, our findings
indicate that binary systems may routinely emerge from common envelope phases
with non-zero eccentricities that were excited by the dynamical friction forces
that drove their orbital tightening.

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The categories of this paper are: econ
9
The categories of this paper are: nlin
30
The categories of this paper are: q-alg
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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: hep-lat
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The categories of this paper are: hep-ex
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The categories of this paper are: chem-ph
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The categories of this paper are: gr-qc
0
The categories of this paper are: hep-ph
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The categories of this paper are: physics
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The categories of this paper are: nucl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: adap-org
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The categories of this paper are: hep-th
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The categories of this paper are: dg-ga