The Exomoon Corridor for Multiple Moon Systems

TL;DR

This paper extends the concept of the exomoon corridor to multi-moon systems using N-body simulations, revealing its applicability, potential observational biases, and evidence of exomoon prevalence in Kepler data.

Contribution

It demonstrates that the exomoon corridor effect applies to systems with multiple moons and explores the implications for exomoon detection and system stability.

Findings

The exomoon corridor relationship holds for systems with up to 5 moons.

An observational bias favors detection of systems with fewer or less massive moons.

Kepler data shows the exomoon corridor distribution, suggesting many moons may exist in the field.

Abstract

Recently Kipping (2021) identified the so-called "exomoon corridor", a potentially powerful new tool for identifying possible exomoon hosts, enabled by the observation that fully half of all planets hosting an exomoon will exhibit transit timing variation (TTV) periodicities of 2-4 epochs. One key outstanding problem in the search for exomoons, however, is the question of how well the methods we have developed under the single moon assumption extend to systems with multiple moons. In this work we use $N$-body simulations to examine the exomoon corridor effect in the more general case of $N \geq 1$ moons, generating realistic TTVs produced by satellite systems more akin to those seen in the outer Solar System. We find that indeed the relationship does hold for systems with up to 5 moons in both resonant and non-resonant chain configurations. Our results suggest an observational bias against finding systems with large numbers of massive moons; as the number of moons increases, total satellite mass ratios are generally required to be significantly lower in order to maintain stability, or architectures must be more finely tuned to survive. Moons produced in impact or capture scenarios may therefore dominate early detections. Finally, we examine the distribution of TTV periods measured for a large number of Kepler Objects of Interest (KOIs) and find the same characteristic exomoon corridor distribution in several cases. This could be dynamical evidence for an abundance of moons in the field, though we caution against strong inferences based on this result.