On the Likelihood of Planet Formation in Close Binaries

TL;DR

This paper investigates how the truncation of protoplanetary disks in close binary star systems affects the likelihood of planet formation, showing that planets can still form under certain binary conditions.

Contribution

It introduces a method to assess the feasibility of planet formation in close binaries based on orbital parameters and demonstrates that planet formation remains possible despite disk truncation.

Findings

Planets are likely to form in close binaries with certain orbital parameters.

Disk truncation reduces available material but does not prevent planet formation in many cases.

A quantitative measure of planet formation feasibility based on binary parameters is proposed.

Abstract

To date, several exoplanets have been discovered orbiting stars with close binary companions (a~<30 AU). The fact that planets can form in these dynamically challenging environments implies that planet formation must be a robust process. The initial protoplanetary disks in these systems from which planets must form should be tidally truncated to radii of a few AU, which indicates that the efficiency of planet formation must be high. Here, we examine the truncation of circumstellar protoplanetary disks in close binary systems, studying how the likelihood of planet formation is affected over a range of disk parameters. If the semimajor axis of the binary is too small or its eccentricity is too high, the disk will have too little mass for planet formation to occur. However, we find that the stars in the binary systems known to have planets should have once hosted circumstellar disks that were capable of supporting planet formation despite their truncation. We present a way to characterize the feasibility of planet formation based on binary orbital parameters such as stellar mass, companion mass, eccentricity and semi-major axis. Using this measure, we can quantify the robustness of planet formation in close binaries and better understand the overall efficiency of planet formation in general.