Characterizing the Orbital and Dynamical State of the HD 82943 Planetary System With Keck Radial Velocity Data

http://arxiv.org/abs/1306.0687

Characterizing the Orbital and Dynamical State of the HD 82943 Planetary System With Keck Radial Velocity Data


We present an updated analysis of radial velocity data of the HD 82943 planetary system based on 10 years of measurements obtained with the Keck telescope. Previous studies have shown that the HD 82943 system has two planets that are likely in 2:1 mean-motion resonance (MMR), with the orbital periods about 220 and 440 days (Lee et al. 2006). However, alternative fits that are qualitatively different have also been suggested, with two planets in a 1:1 resonance (Gozdziewski & Konacki 2006) or three planets in a Laplace 4:2:1 resonance (Beauge et al. 2008). Here we use \c{hi}2 minimization combined with parameter grid search to investigate the orbital parameters and dynamical states of the qualitatively different types of fits, and we compare the results to those obtained with the differential evolution Markov chain Monte Carlo method. Our results support the coplanar 2:1 MMR configuration for the HD 82943 system, and rule out 1:1 and 3-planet Laplace resonance fits. The inclination of the system with respect to the sky plane is well constrained at about 20 degree, and the system contains two planets with masses of about 4.78 MJ and 4.80 MJ (where MJ is the mass of Jupiter) and orbital periods of about 219 and 442 days for the inner and outer planet, respectively. The best fit is dynamically stable with both eccentricity-type resonant angles {\theta}1 and {\theta}2 librating around 0 degree.

Nice to see it pinned down, though pity it is not one of the more "exotic" possibilities. Does nature ever actually build co-orbital planets?

Star - Planet - Debris Disk Alignment in the HD 82943 system: Is planetary system coplanarity actually the norm?
http://arxiv.org/abs/1309.1466

Looks like the star, disk, and planetary system are coplanar.

Possible solution to the riddle of HD 82943 multi-planet system: the three-planet resonance 1:2:5?
http://arxiv.org/abs/1310.7101

Quote :

We carry out a new analysis of the published radial velocity data for the planet-hosting star HD82943. We include the recent Keck/HIRES measurements as well as the aged but much more numerous CORALIE data. We find that the CORALIE radial velocity measurements are polluted by a systematic annual variation which affected the robustness of many previous results. We show that after purging this variation, the residuals still contain a clear signature of an additional ∼1100 days periodicity. The latter variation leaves significant hints in all three independent radial velocity subsets that we analysed: the CORALIE data, the Keck data acquired prior to a hardware upgrade, and the Keck data taken after the upgrade.
We mainly treat this variation as a signature of a third planet in the system, although we cannot rule out other interpretations, such as long-term stellar activity. We find it easy to naturally obtain a stable three-planet radial-velocity fit close to the three-planet mean-motion resonance 1:2:5, with the two main planets (those in the 1:2 resonance) in an aligned apsidal corotation. The dynamical status of the third planet is still uncertain: it may reside in as well as slightly out of the 5:2 resonance. We obtain the value of ∼1075 days for its orbital period and of ∼0.3MJup for its minimum mass, while the eccentric parameters are uncertain.

A third planet, and perhaps a 1:2:5 MMR setup for the system.

Also they get a much weaker constraint on the inclination of the planets, so the case for the system being coplanar with the debris disc is also weaker.

Precise determination of fundamental parameters of six exoplanet host stars and their planets
http://arxiv.org/abs/1406.2173

Revised parameters for the third planet (among others).