We present robust planet occurrence rates for Kepler planet candidates around M stars for planet radii R _ { p } = 0.5 - 4 ~ { } \textrm { R } _ { \oplus } and orbital periods P = 0.5 - 256 days using the approximate Bayesian computation ( ABC ) technique .
This work incorporates the final Kepler DR25 planet candidate catalog and data products and augment them with updated stellar properties using Gaia DR2 and 2MASS PSC .
We analyze a clean sample of 1 , 530 Kepler targets that host 89 associated planet candidates .
These early M-dwarfs and late K-dwarfs were selected from cross-referenced targets using several photometric quality flags from Gaia DR2 and color-magnitude cuts using 2MASS magnitudes .
We identify a habitable zone occurrence rate of f _ { \textrm { HZ } } = 0.38 ^ { +0.04 } _ { -0.05 } for planets with 0.75 - 1.5 R _ { \oplus } size .
We caution that occurrence rate estimates for Kepler ’ s M stars are sensitive to the choice of prior due to the small sample of target stars and planet candidates .
For example , we find an occurrence rate of 8.9 ^ { +1.2 } _ { -0.9 } or 4.8 ^ { +0.7 } _ { -0.6 } planets per M-dwarf ( integrating over R _ { p } = 0.5 - 4 ~ { } \textrm { R } _ { \oplus } and P = 0.5 - 256 days ) for our two choices of prior .
These occurrence rates are greater than those for FGK-dwarf target when compared at the same range of orbital periods , but similar to occurrence rates when computed as a function of equivalent stellar insolation .
This suggests that stellar irradiance has a significant and possibly dominant role in planet formation processes regardless of spectral type .
Combining our result with recent studies of exoplanet architectures indicates that most , and potentially all , early-M dwarfs harbor planetary systems .