The orbital eccentricity distribution of planets orbiting M dwarfs

Abstract

The orbital eccentricities of exoplanets orbiting M dwarf stars may significantly affect their habitability but are unknown. We extract this eccentricity distribution using a sample of transiting planets orbiting M dwarfs detected by NASA's Kepler Mission with stellar density measurements. We find planets in apparently single-transiting systems are typically more eccentric than planets in multiply transiting systems. The single- transit data prefer an eccentricity model composed of two distinct dynamically warmer and cooler subpopulations over three single-component models. With known planet demographics, we estimate the eccentricity distribution for the population of early- to mid-M dwarf planets in the local neighborhood, with implications for planetary formation and follow-up observations. Comparing our findings with similar studies for Sunlike stars suggests common dynamical excitation mechanisms.