AAS 201st Meeting, January, 2003
Session 24. Planetary Systems I
Oral, Monday, January 6, 2003, 10:00-11:30am, 606-607

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[24.04] On the Dynamical State of New Multi-Planet Systems.

L. Kiseleva-Eggleton (St. Mary's College of California), E. Bois, N. Rambaux (Bordeaux Observatory), R. Dvorak (Institute of Astronomy, University of Vienna), E.J. Rivera (Carnegie Institution of Washington)

In order to distinguish between regular and chaotic planetary orbits we apply a new technique called MEGNO (Mean Exponential Growth factor for Nearby Orbits) in a wide neighbourhood of orbital parameters determined using standard two-body Keplerian fits for HD 12661, HD 38529, HD 37124, HD 160691 planetary systems. We show that the currently announced orbital parameters place these systems in very different situations from the point of view of dynamical stability. While HD 38529 and HD 37124 are located within large stability zones in the phase space around their determined orbits, the preliminary orbits in HD 160691, including most self-consistent fits to current radial velocity data, are highly unstable. However some new fits for this system, where the outermost planet is very massive and orbiting the star on a rather distant nearly circular orbit are stable. Also there are a few stable configurations located not very far in the parameter space from the announced parameters of the system and associated with the 2:1 mean motion resonance. It looks as if a high eccentricity of the outermost planet ec>0.7 is an important stabilizing factor in these cases. The orbital parameters of the HD 12661 planets are located in a border region between stable and unstable dynamical regimes, so while its currently determined orbital parameters produce stable regular orbits, a minor change within the margin of error of just one parameter may result in a chaotic dynamical system.

The author(s) of this abstract have provided an email address for comments about the abstract: lkissele@stmarys-ca.edu

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