Iron abundance correlations and an occurrence distribution discrepancy from ongoing planet migration

TL;DR

This paper investigates the relationship between stellar iron abundance and planet migration, revealing that high eccentricity migration and planet-star mergers are linked to stellar metallicity and system architecture, impacting planetary distribution.

Contribution

It introduces new patterns in planet-star systems based on stellar [Fe/H] and companions, supporting eccentric migration as a key process in planetary evolution.

Findings

Iron-rich single stars host planets with higher eccentricities.

Stars with stellar companions tend to be iron-rich.

Giant planets migrate into stars faster than medium planets.

Abstract

Whether the higher occurrence of giant planets being hosted by metal-rich versus metal-poor stars results from formation or from "pollution" has been a question of intense debate. We present new patterns that emerge when planet/star systems are separated by stellar [Fe/H], and when systems with stellar companions are separated out. These differences can best be explained if the onset of high eccentricity planet migration is also a time when planet are sent into merge with the star. Planet migration into the star is likely a complementary explanation to the view that systems with higher initial iron abundance form more planets, and that more crowded planets are more likely to scatter into eccentric orbits. Planets of iron-rich single stars have eccentricity distributions that are higher than planets of iron-poor single stars (where "rich" and "poor" are stars whose [Fe/H] is above and below solar, respectively). Stars with planets that have a stellar companion comprise a third population of systems in which the stars are preferentially iron-rich. We describe new patterns that are best explained by eccentric planet migration being associated with other planets migrating into the star. Though medium planets are more numerous than giant planets at periods greater than three days, giant planets are more numerous than medium planets at the shortest periods. Since giant planets migrate into the star faster, we show this as evidence of giant planet migration. Planet migration into the star is certain to be an important part of planetary system evolution.