The Occurrence of Rocky Habitablezone Planets around Solarlike Stars from Kepler Data
Abstract
We present the occurrence rates for rocky planets in the habitable zones (HZs) of mainsequence dwarf stars based on the Kepler DR25 planet candidate catalog and Gaiabased stellar properties. We provide the first analysis in terms of stardependent instellation flux, which allows us to track HZ planets. We define η_{⊕} as the HZ occurrence of planets with radii between 0.5 and 1.5 R_{⊕} orbiting stars with effective temperatures between 4800 and 6300 K. We find that η_{⊕} for the conservative HZ is between ${0.37}_{0.21}^{+0.48}$ (errors reflect 68% credible intervals) and ${0.60}_{0.36}^{+0.90}$ planets per star, while the optimistic HZ occurrence is between ${0.58}_{0.33}^{+0.73}$ and ${0.88}_{0.51}^{+1.28}$ planets per star. These bounds reflect two extreme assumptions about the extrapolation of completeness beyond orbital periods where DR25 completeness data are available. The large uncertainties are due to the small number of detected small HZ planets. We find similar occurrence rates between using Poisson likelihood Bayesian analysis and using Approximate Bayesian Computation. Our results are corrected for catalog completeness and reliability. Both completeness and the planet occurrence rate are dependent on stellar effective temperature. We also present occurrence rates for various stellar populations and planet size ranges. We estimate with 95% confidence that, on average, the nearest HZ planet around G and K dwarfs is ∼6 pc away and there are ∼4 HZ rocky planets around G and K dwarfs within 10 pc of the Sun.
 Publication:

The Astronomical Journal
 Pub Date:
 January 2021
 DOI:
 10.3847/15383881/abc418
 arXiv:
 arXiv:2010.14812
 Bibcode:
 2021AJ....161...36B
 Keywords:

 Exoplanets;
 498;
 Astrophysics  Earth and Planetary Astrophysics;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 To appear in The Astronomical Journal