The Kepler Dichotomy Among the M Dwarfs: Half of Systems Contain Five or More Coplanar Planets

We present a statistical analysis of the Kepler M dwarf planet hosts, with a particular focus on the fractional number of systems hosting multiple transiting planets. We manufacture synthetic planetary systems within a range of planet multiplicity and mutual inclination for comparison to the Kepler yield. Similarly to studies of Kepler exoplanetary systems around more massive stars, we report that the number of singly transiting planets found by Kepler is too high to be consistent with a single population of multi-planet systems, a finding that cannot be attributed to selection biases. To account for the excess singleton planetary systems we adopt a mixture model and find that 53 ± 10% of planetary systems are either single or contain multiple planets with large mutual inclinations. The other 47 ± 10% of systems contain planets with mutual inclinations of 2.°0 ± 1.°3. This mutual inclination range is consistent with studies of transit durations within multiply transiting systems. The mixture model is preferred 8:1 to a model with only one architecture. Thus, we find that the so-called “ Kepler dichotomy” holds for planets orbiting M dwarfs as well as Sun-like stars.