Architectures of exoplanetary systems – I. A clustered forward model for exoplanetary systems around Kepler’s FGK stars

Abstract

Observations of exoplanetary systems provide clues about the intrinsic distribution of planetary systems, their architectures, and how they formed. We develop a forward modeling framework for generating populations of planetary systems and "observed" catalogs by simulating the Kepler detection pipeline (SysSim). We compare our simulated catalogs to the Kepler DR25 catalog of planet candidates, updated to include revised stellar radii from Gaia DR2. We constrain our model based on the observed 1-D marginal distributions of orbital periods, period ratios, transit depths, transit depth ratios, transit durations, transit duration ratios, and transit multiplicities. Models assuming planets with independent periods and sizes do not adequately account for the properties of the multi-planet systems. Instead, a clustered point process model for exoplanet periods and sizes provides a significantly better description of the Kepler population, particularly the observed multiplicity and period ratio distributions. We find that 0.56 +0.18 −0.15 of FGK stars have at least one planet larger than 0.5R ⊕ between 3 and 300 days. Most of these planetary systems (∼ 98%) consist of one or two clusters with a median of three planets per cluster. We find that the Kepler dichotomy is evidence for a population of highlyinclined planetary systems and is unlikely to be solely due to a population of intrinsically single planet systems. We provide a large ensemble of simulated physical and observed catalogs of planetary systems from our models, as well as publicly available code for generating similar catalogs given user-defined parameters.

Occurrence Rates of Planets Orbiting FGK Stars: Combining Kepler DR25, Gaia DR2, and Bayesian Inference

“…When using the Dirichlet prior, the observed number of M dwarf planet candidates is also consistent with as few as half of M dwarfs hosting planetary systems. Recently, He et al (2019) investigated the architectures of planetary systems around Sun-like (FGK) stars with a clustered point process model built in the same SysSim framework as this study. He et al (2019) report a 68.3% credible interval for the multiplicity of 2.28 +0.94 0.53 .…”

“…Recently, He et al (2019) investigated the architectures of planetary systems around Sun-like (FGK) stars with a clustered point process model built in the same SysSim framework as this study. He et al (2019) report a 68.3% credible interval for the multiplicity of 2.28 +0.94 0.53 . Since this is less than the in-tegrated rate of M dwarf planets (for both out priors), even assigning every M dwarf such a planetary system would not be sufficient to explain the number of M dwarf planets detected by Kepler.…”

Joint Radial Velocity and Direct Imaging Planet Yield Calculations. I. Self-consistent Planet Populations

“…We do not apply an additional multiplicative factor representing the fraction of stars with planets -e.g. that there exists a population of stars with no planets in excess of a Poisson distribution, as is sometimes done in the literature (Mulders et al 2018;Zhu et al 2018;He et al 2019). In other words, we effectively assume the fraction of stars with planets per region is unity, and that the average number of stars per planet per region holds for all planets and that the individual number of planets per star per region follows a Poisson distribution which can include zero planets (see also 4).…”

Occurrence and Architecture of Kepler Planetary Systems as Functions of Stellar Mass and Effective Temperature

“…By assuming planets in multi-planet systems are in coplanar orbits, Fressin et al (2013) and Petigura et al (2013) have found over 50% of Sun-like stars have Kepler -like planets (F p > 0.5). Recently, Zhu et al (2018), Mulders et al (2018), and He et al (2019) have modified the F p estimate by taking into account non-coplanar planetary systems.…”