Conditions of Dynamical Stability for the HD 160691 Planetary System

Astrophysics, abstract
astro-ph/0301528

From: Eric Bois <eric.bois@observ.u-bordeaux.fr>

Date: Mon, 27 Jan 2003 10:21:23 GMT   (337kb)

Authors:
Eric Bois (1),
Ludmila Kiseleva-Eggleton (2),
Nicolas Rambaux (1),
Elke Pilat-Lohinger (3) ((1) Observatoire Aquitain des Sciences de l’Univers, Bordeaux, France, (2) St. Mary’s College of California, Moraga, USA, (3) Institute of Astronomy, University of Vienna, Austria)

Comments: 7 pages, 7 figures, 1 table

This paper presents a global dynamics analysis in the 3-D orbital parameter
space related to the HD 160691 planetary system whose orbital parameters of the
outer planet are yet uncertain. We make into evidence a stabilizing mechanism
that could be the key to its existence. We show that the orbital parameters may
allow the existence of a rather wide stability zone in the semi-major axes
parameter space. This stability zone is only possible as the result of a 2:1
mean motion resonance coupled with adequate relative positions of the planets
on their orbits avoiding close approaches in the closeness of their periastron.
The mechanism itself is preserved by librations of the mean motion resonance
variables while the longitudes of periapse on average precess at the same rate.
We conclude that in order to be dynamically stable, the HD 160691 planetary
system has to satisfy the following conditions: (1) a 2:1 mean motion resonance
combined with (2) an apsidal secular resonance in (3) a configuration where the
two apsidal lines are anti-aligned, and (4) high eccentricity for the outer
orbit. In this orbital topology, the HD 160691 system and its mechanism have
revealed resources of the 2:1 orbital resonances that have not been observed
nor analyzed before. We also show that there is an upper limit for planetary
masses due to the dynamical stability mechanism. We obtained our results using
a new technique called MEGNO and verified them with the Fast Lyapunov Indicator
technique (FLI).

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