TY - JOUR
T1 - A Universal Break in the Planet-to-star Mass-ratio Function of Kepler MKG Stars
AU - Pascucci, Ilaria
AU - Mulders, Gijs D.
AU - Gould, Andrew
AU - Fernandes, Rachel
N1 - Funding Information:
The authors thank Savita Mathur and Daniel Huber for sharing some of their results on stellar properties in advance of publication. I.P. also thanks Bertram Bitsch for a useful discussion on pebble accretion models. This Letter includes data collected by the Kepler mission. Funding for the Kepler mission is provided by the NASA Science Mission directorate. This material is based upon work supported by the National Aeronautics and Space Administration under Agreement No. NNX15AD94G for the program Earths in Other Solar Systems. The results reported herein benefited from collaborations and/ or information exchange within NASA’s Nexus for Exoplanet System Science (NExSS) research coordination network sponsored by NASA’s Science Mission Directorate. Facility: Kepler.
Publisher Copyright:
© 2018. The American Astronomical Society. All rights reserved..
PY - 2018/4/1
Y1 - 2018/4/1
N2 - We follow the microlensing approach and quantify the occurrence of Kepler exoplanets as a function of planet-to-star mass ratio, q, rather than planet radius or mass. For planets with radii ∼1-6 R ⊕ and periods <100 days, we find that, except for a normalization factor, the occurrence rate versus q can be described by the same broken power law with a break at ∼3 10-5 independent of host type for hosts below 1 Mo. These findings indicate that the planet-to-star mass ratio is a more fundamental quantity in planet formation than planet mass. We then compare our results to those from microlensing for which the overwhelming majority satisfies the M host < 1 Mo criterion. The break in q for the microlensing planet population, which mostly probes the region outside the snowline, is ∼3-10 times higher than that inferred from Kepler. Thus, the most common planet inside the snowline is ∼3-10 times less massive than the one outside. With rocky planets interior to gaseous planets, the solar system broadly follows the combined mass-ratio function inferred from Kepler and microlensing. However, the exoplanet population has a less extreme radial distribution of planetary masses than the solar system. Establishing whether the mass-ratio function beyond the snowline is also host type independent will be crucial to build a comprehensive theory of planet formation.
AB - We follow the microlensing approach and quantify the occurrence of Kepler exoplanets as a function of planet-to-star mass ratio, q, rather than planet radius or mass. For planets with radii ∼1-6 R ⊕ and periods <100 days, we find that, except for a normalization factor, the occurrence rate versus q can be described by the same broken power law with a break at ∼3 10-5 independent of host type for hosts below 1 Mo. These findings indicate that the planet-to-star mass ratio is a more fundamental quantity in planet formation than planet mass. We then compare our results to those from microlensing for which the overwhelming majority satisfies the M host < 1 Mo criterion. The break in q for the microlensing planet population, which mostly probes the region outside the snowline, is ∼3-10 times higher than that inferred from Kepler. Thus, the most common planet inside the snowline is ∼3-10 times less massive than the one outside. With rocky planets interior to gaseous planets, the solar system broadly follows the combined mass-ratio function inferred from Kepler and microlensing. However, the exoplanet population has a less extreme radial distribution of planetary masses than the solar system. Establishing whether the mass-ratio function beyond the snowline is also host type independent will be crucial to build a comprehensive theory of planet formation.
KW - data analysis-planetary systems-planets and satellites
KW - formation
KW - methods
UR - http://www.scopus.com/inward/record.url?scp=85045575517&partnerID=8YFLogxK
U2 - 10.3847/2041-8213/aab6ac
DO - 10.3847/2041-8213/aab6ac
M3 - Article
AN - SCOPUS:85045575517
SN - 2041-8205
VL - 856
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 2
M1 - L28
ER -