Extreme exomoons in WASP-49 Ab: dynamics and detectability

TL;DR

This paper investigates the stability and detectability of potential exomoons around WASP-49Ab, considering complex physical effects, and identifies conditions under which such moons could survive in a challenging environment.

Contribution

It provides a comprehensive analysis of exomoon stability around WASP-49Ab using advanced simulations, including effects of oblateness, relativity, and stellar perturbations, highlighting key factors for their potential survival.

Findings

Stable exomoons are likely in close, low-eccentricity orbits near the Roche limit.

Eccentricity and orbital distance significantly affect moon stability.

Resonance destabilizes moons near 1.4 planetary radii with slight planetary eccentricities.

Abstract

WASP-49Ab, a low-density, Saturn-like planet in a tight orbit around a Sun-like star within a wide binary system, is a compelling candidate for hosting a volcanic moon, as suggested by the detection of Doppler-shifted sodium.This study evaluates the stability of potential satellites around WASP-49Ab under the influence of planetary oblateness, relativistic effects, and perturbations from a close companion star, focusing on their impact on light curve parameters such as transit duration and impact parameter variations, driven by the evolution of the planet's orbit in this extreme environment. Using N-body simulations and semi-analytical methods, we analysed moon's dynamics across varied initial conditions and gravitational frameworks including the potential of an oblate planet and the effects of the general relativity. We find that `selenity', a moon survival indicator, is high in close orbits with low eccentricity, near the Roche limit, especially for masses greater than Io's. Stability decreases as eccentricity or distance from the planet increases. Additionally, We observe a strong destabilising resonance near 1.4 planetary radii when planetary eccentricities are slightly greater than zero. This study confirms the potential for stable exomoons around WASP-49Ab despite its hostile environment, emphasizing the importance of incorporating diverse physical effects in stability analyses, aiding future detection efforts.