Secular Behavior of Exoplanetary Systems: Self-Consistency and Comparisons With The Planet-Planet Scattering Hypothesis
Venue
The Astrophysics Journal, vol. 146 (2011), pp. 53
Publication Year
2011
Authors
Miles Timpe, Rory Barnes, Ravikumar Kopparapu, Sean N. Raymond, Richard Greenberg, Noel Gorelick
BibTeX
Abstract
Planet-planet scattering has been suggested as a mechanism to explain the
disproportionate number of planet-planet pairs found to lie on or near an apsidal
separatrix, in which one planet's eccentricity periodically drops to near-zero. We
present the results of numerical simulations of 2-planet systems having arisen from
dynamically unstable 3-planet systems. We show that the distribution of
near-separatrix systems arising after an instability is consistent with the
observed systems, further strengthening the planet-planet scattering hypothesis. We
also note that many observed systems have been found near their extreme
eccentricity values. Such a pattern may suggest a bias in exoplanet observations,
as planets should have an equal probability of being discovered at any point in
their secular cycle. We test this possibility by numerically integrating known
multiplanet systems and determining the relative time each planet spends in a given
eccentricity range and then comparing this distribution of eccentricity values to
the observational uncertainty. We find that planets tend to spend more time near
their minimum and maximum values as they represent turning points in the
oscillations. Moreover, the uncertainties for many eccentricities are so large that
we cannot make strong statements regarding the possibility that planets are being
discovered at their extreme eccentricities too often. However, as uncertainties
become smaller and more multiplanet systems are discovered, this potential bias
should be revisited.
