Architectures of Planetary Systems II: Trends with Host Star Mass and Metallicity

TL;DR

This study extends the architecture-based classification of planetary systems to examine host-star mass and metallicity, using an updated dataset of 5881 planets in 4289 systems. By applying a $k$-nearest-neighbors permutation framework to compare host-star distributions across $N\ge 3$ categories against source populations, the authors find that total planetary mass correlates with host-star mass and metallicity, and there is an upper mass limit around $M/M_{\ast} \sim 0.03$ (with disk-stability considerations suggesting $M_d/M_{\ast} \sim 0.1$). Jovian planets are less common around low-mass and low-metallicity stars, but overall planetary-system architectures show limited direct dependence on host properties, with notable exceptions for super-puffs and certain hot-jupiter configurations. The work strengthens the link between host-star properties and planet mass while highlighting the role of dynamical processes in shaping architectures, and it underscores the need for larger, more complete samples, especially at the low-mass end, to refine these trends.

Abstract

The current census of planetary systems displays a wide range of architectures. Extending earlier work, this paper investigates the correlation between our classification framework for these architectures and host stellar properties. Specifically, we explore how planetary system properties depend on stellar mass and stellar metallicity. This work confirms previously detected trends that jovian planets are less prevalent for low-mass and low-metallicity stars. We also find new, but expected trends such as that the total mass in planets increases with stellar mass, and that observed planetary system masses show an upper limit that is roughly consistent with expectations from the stability of circumstellar disks. We tentatively identify potential unique trends in the host stars of super-puffs and hot jupiters and a possible subdivision of the class of hot jupiter systems. In general, we find that system architectures are not overly dependent on host star properties.

Figures (6)

• Figure 1: Abridged quick-reference chart for our classification of planetary system architectures presented in Paper I. Each row corresponds to one planetary system, with horizontal spacing corresponding to orbital period on a log scale and point sizes corresponding to planet size. Colors correspond to planet type: jupiters in red, neptunes in yellow, sub-neptunes in blue, and earths in green.
• Figure 2: Masses and metallicities of the exoplanet host star population compared with the total planet mass in each system. Top left, bottom left, and bottom right are density contour plots where each contour corresponds to 0.5$\sigma$, with the outermost contour being 2.5$\sigma$, or 99% of host stars. Outlier systems are marked with X's. Top right is a histogram of mass ratios of total planet mass divided by host mass.
• Figure 3: Masses and metallicities of exoplanet host stars divided by planet size and number. Square markers indicate the median points of each distribution. Shaded areas are $1\sigma$ density contours; solid lines are $2\sigma$ contours, and X's are $>2\sigma$ outliers. Panel (a): population divided into subsets based on whether the largest detected planet is a jupiter (red), a neptune (gold), a sub-neptune (blue), or an earth (green). Panel (b): population divided into subsets with no jupiters (black), exactly one jupiter (red), exactly two jupiters (purple), and three or more jupiters (dark yellow). (The highest number in our data set is four.)
• Figure 4: Masses and metallicities of CPP host stars (black) compared with two of our potential source populations: all exoplanet hosts with jupiters (red) and all host stars without jupiters (blue).
• Figure 5: Comparison of host star masses and metallicities of $N\space\ge\space3$ categories of exoplanet systems (black points), compared with two of our potential source populations: all exoplanet hosts with jupiters (red) and all host stars without jupiters (blue).