On the Age and Metallicity of Planet-hosting Triple Star Systems

TL;DR

This study analyzes the ages and metallicities of triple star systems hosting exoplanets, suggesting they are generally younger and have solar-like metallicities, with implications for planet formation and system stability.

Contribution

It provides the first statistical analysis of ages and metallicities of triple star systems with exoplanets, highlighting potential selection effects and stability issues.

Findings

Host systems are on average younger than typical stars.

Metallicities are broadly solar-like, not necessarily metal-rich.

Possible selection biases due to stellar mass and orbital stability.

Abstract

We present a statistical analysis of the ages and metallicities of triple stellar systems that are known to host exoplanets. With controversial cases disregarded, so far 27 of those systems have been identified. Our analysis, based on an exploratory approach, shows that those systems are on average notably younger than stars situated in the solar neighborhood. Though the statistical significance of this result is not fully established, the most plausible explanation is a possible double selection effect due to the relatively high mass of planet-hosting stars of those systems (which spend less time on the main-sequence than low-mass stars) and that planets in triple stellar systems may be long-term orbitally unstable. The stellar metallicities are on average solar-like; however, owing to the limited number of data, this result is not inconsistent with the previous finding that stars with planets tend to be metal-rich as the deduced metallicity distribution is relatively broad.