Examining Kepler Circumbinary Planetary Systems With Single Planets

A dynamical stability study of Kepler Circumbinary planetary systems with one planet

Authors:

Chavez et al

Abstract:

To date, 17 circumbinary planets have been discovered. In this paper, we focus our attention on the stability of the Kepler circumbinary planetary systems with only one planet, i.e. Kepler-16, Kepler-34, Kepler-35, Kepler-38, Kepler-64 and Kepler-413. In addition to their intrinsic interest, the study of such systems is an opportunity to test our understanding of planetary system formation and evolution around binaries. The investigation is done by means of numerical simulations. We perform numerical integrations of the full equations of motion of each system with the aim of checking the stability of the planetary orbit. The investigation of the stability of the above systems consists of three numerical experiments. In the first one, we perform a long-term (1 Gyr) numerical integration of the nominal solution of the six Kepler systems under investigation. In the second experiment, we look for the critical semimajor axis of the six planetary orbits, and finally, in the third experiment, we construct two-dimensional stability maps on the eccentricity–pericentre distance plane. Additionally, using numerical integrations of the nominal solutions we checked if these solutions were close to the exact resonance.

Modelling the Circumbinary Planets of Kepler-38

Modelling Circumbinary Planets: The case of Kepler-38

Authors:

Kley et al

Abstract:

Recently, a number of planets orbiting binary stars have been discovered by the Kepler space telescope. In a few systems the planets reside close to the dynamical stability limit. Due to the difficulty of forming planets in such close orbits, it is believed that they have formed further out in the disk and migrated to their present locations. Our goal is to construct more realistic models of planet migration in circumbinary disks, and to determine the final position of these planets. In our work, we focus on the system Kepler-38. The evolution of the circumbinary disk is studied using two-dimensional hydrodynamical simulations. We study locally isothermal disks as well as more realistic models with viscous heating, radiative cooling from the disk surfaces, and radiative diffusion in the disk mid plane. After the disk has been brought into equilibrium, a 115 Earth-mass planet is embedded and its evolution is followed. In all cases the planets stop inward migration near the inner edge of the disk. In isothermal disks with a typical disk scale height of H/r = 0.05, the final outcome agrees very well with the observed location of planet Kepler-38b. For the radiative models, the disk thickness and location of the inner edge is determined by the mass in the system. For surface densities in the order of 3000 g/cm^2 at 1 AU, the inner gap lies close to the binary and planets stop in the region between the 5:1 and 4:1 mean-motion resonances with the binary. A model with a disk with approximately a quarter of the mass yields a final position very close to the observed one. For planets migrating in circumbinary disks, the final position is dictated by the structure of the disk. Knowing the observed orbits of circumbinary planets, radiative disk simulations with embedded planets can provide important information on the physical state of the system during the final stages of its evolution.