Dynamical stability of the Gliese 581 exoplanetary system

Abstract

Using numerical methods we investigate the dynamical stability of the Gliese 581 exoplanetary system. The system is known to harbour four planets (b-e). The existence of another planet (g) in the liquid water habitable zone of the star is debated after the latest analyses of the radial velocity (RV) measurements. We integrated the 4 and 5-planet model of Vogt et al. (AN 333, 561-575, 2012) with initial circular orbits. To characterize stability, the maximum eccentricity was used that the planets reached over the time of the integrations and the LCI and RLI to identify chaotic motion. Since circular orbits in the RV fits seem to be a too strong restriction and the true orbits might be elliptic, we investigated the stability of the planets as a function of their eccentricity. The integration of the circular 4-planet model shows that it is stable on a longer timescale for even an inclination i = 5°. A fifth planetary body in the 4-planet model could have a stable orbit between the two super-Earth sized planets c and d, and beyond the orbit of planet d, although another planet would likely only be stable on circular or near-circular orbit in the habitable zone of the star. Gliese 581 g in the 5-planet model would have a dynamically stable orbit, even for a wider range of orbital parameters, but its stability is strongly dependent on the eccentricity of planet d. The low-mass planet e, which quickly became unstable in eccentric models, remains stable in the circular 4-planet model, but the stable region around its initial semi-major axis and eccentricity is rather small. The stability of the inner planets e and c is dependent on the eccentricity of the Neptune-size planet b. The outermost planet d is far away from the adjacent planet c to considerably influence its stability, however, the existence of a planet between the two super-Earth planets c and d constrains its eccentricity.

8 pages, 3 tables, 8 figures; accepted for publication in MNRAS

References in corpus (13)

• Habitable planets around the star Gl 581?
• The HARPS search for southern extra-solar planets XI. Super-Earths (5 & 8 M_Earth) in a 3-planet system
• The impact of red noise in radial velocity planet searches: Only three planets orbiting GJ581?
• A DEBRIS Disk Around The Planet Hosting M-star GJ581 Spatially Resolved with Herschel
• Dynamical evolution and spin-orbit resonances of potentially habitable exoplanets. The case of GJ 581d
• Bayesian re-analysis of the radial velocities of Gliese 581. Evidence in favour of only four planetary companions
• A new analysis of the GJ581 extrasolar planetary system
• GJ 581 update: Additional Evidence for a Super-Earth in the Habitable Zone
• An investigation into the radial velocity variability of GJ 581 - On the significance of GJ 581g
• The HARPS search for southern extra-solar planets XXXII. Only 4 planets in the Gl~581 system
• Solving Linearized Equations of the $N$-body Problem Using the Lie-integration Method
• Aliases of the first eccentric harmonic : Is GJ 581g a genuine planet candidate?
• Counting the number of planets around GJ 581. False positive rate of Bayesian signal detection methods

Cited by in corpus (4)

• Fast Bayesian Inference for Exoplanet Discovery in Radial Velocity Data
• System Architecture and Planetary Obliquity: Implications for Long-Term Habitability
• The CARMENES search for exoplanets around M dwarfs. Revisiting the GJ 581 multi-planetary system with new Doppler measurements from CARMENES, HARPS, and HIRES
• An alternative stable solution for the Kepler-419 system, obtained with the use of a genetic algorithm