The Kepler-102 system has five transiting planets, b-f, with orbital periods in the range of 5-28 days. It is one of the many closely-packed Kepler multi-planet systems that exhibit dynamical instabilities on <100 Myr timescales when numerically integrated with a range of plausible planet masses and small initial eccentricities. Given that the host star is estimated to be >2 Gyr old, the observed system likely avoided such short-timescale instabilities. We investigate how planet-planet perturbations and dynamical evolution considerations can help constrain the planet masses in this system, particularly those of the smallest innermost planets. Like many Kepler systems, the Kepler-102 planets lie near, but not librating in, mutual mean motion resonances (MMRs). For example, planet b's orbital period lies in-between the 2:1 internal MMR of planet d and the 4:3 internal MMR of planet c. Making use of analytical and numerical resonance width estimates, we find that the masses of planets b, c, and d would have to be implausibly large given their observed sizes for resonance effects (either through interaction with individual resonances or through chaotic dynamics of overlapping resonances) to be the source of instability. This means that the MMRs are not the dominant source of instabilities in numerical integrations, and thus the resonances provide only very weak constraints on the planet masses. We instead find that the instabilities in the numerical simulations of the Kepler-102 system are driven by secular chaos. We combine secular chaos theory with numerical investigations to constrain the range of masses and eccentricities for the Kepler-102 system that minimize dynamical instabilities driven by these effects.
American Astronomical Society Meeting Abstracts #235
- Pub Date:
- January 2020