Dynamics and Eccentricity Formation of Planets in OGLE-06-109L System

TL;DR

This paper investigates the dynamics and formation scenarios of the OGLE-06-109L planetary system, analyzing stability, potential for habitable planet formation, and possible evolutionary pathways for the observed eccentricities.

Contribution

It introduces a detailed analysis of the system's orbital stability and explores three formation scenarios, assessing their likelihood and implications for eccentricity development.

Findings

System stability depends on eccentricities satisfying eb^2 + ec^2 <= 0.3^2.

Earth-sized planets could form and remain stable in the habitable zone.

The probability of 3:1 MMR trapping is low (~3%), making it an unlikely formation scenario.

Abstract

Recent observation of microlensing technique reveals two giant planets at 2.3 AU and 4.6 AU around the star OGLE-06-109L. The eccentricity of the outer planet (ec) is estimated to be 0.11(+0.17,-0.04), comparable to that of Saturn (0.01-0.09). The similarities between the OGLE-06-109L system and the solar system indicate that they may have passed through similar histories during their formation stage. In this paper we investigate the dynamics and formation of the orbital architecture in the OGLE-06-109L system. For the present two planets with their nominal locations, the secular motions are stable as long as their eccentricities (eb; ec) fulfill eb^2 + ec^2 < = 0.3^2. Earth-size bodies might be formed and are stable in the habitable zone (0.25AU-0.36AU) of the system. Three possible scenarios may be accounted for formation of eb and ec: (i) convergent migration of two planets and the 3:1 MMR trapping; (ii) planetary scattering; (iii) divergent migration and the 3:1 MMR crossing. As we showed that the probability for the two giant planets in 3:1 MMR is low (~3%), scenario (i) is less likely. According to models (ii) and (iii), the final eccentricity of inner planet (eb) may oscillate between [0-0.06], comparable to that of Jupiter (0.03-0.06). An inspection of eb, ec secular motion may be helpful to understand which model is really responsible for the eccentricity formation.