Wei Zhu (祝伟)
Astrophysical Journal 873, 8 Link to Article [DOI: 10.3847/1538-4357/ab0205 ]
Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8, Canada

We study the influence of stellar metallicity on the fraction of stars with planets (i.e., the occurrence rate of planetary systems) and the average number of planets per star (i.e., the occurrence rate of planets). The former directly reveals the planet formation efficiency, whereas the latter reveals the final product of formation and evolution. We show that these two occurrence rates have different dependences on stellar metallicity. Specifically, the fraction of stars with planets rises gradually with metallicity, from ~25% to ~36% for 0.4 dex of [Fe/H] for all Kepler-like planets (period P < 400 days and radius ). The average number of planets per star reaches a plateau (or possibly starts declining) at [Fe/H]  0.1. This is plausibly caused by the emergence of distant giant planets at high metallicities, given that the close-in small planets and the distant giants preferentially coexist in the same system.