Exomoons in Systems with a Strong Perturber: Applications to α Cen AB

Status Report From: e-Print archive
Posted: Tuesday, May 4, 2021

Billy Quarles, Siegfried Eggl, Marialis Rosario-Franco, Gongjie Li

The presence of a stellar companion can place constraints on occurrence and orbital evolution of satellites orbiting exoplanets, i.e., exomoons. In this work we revise earlier orbital stability limits for retrograde orbits in the case of a three body system consisting of star-planet-satellite. The latter reads acritsat≈0.668(1−1.236ep) for ep≤0.8 in units of the Hill Radius and represents the lower critical orbit as a function of the planetary eccentricity ep. A similar formula is determined for exomoons hosted by planets in binary star systems, where ep is replaced with the components of free and forced eccentricity from secular orbit evolution theory. By exploring the dynamics of putative exomoons in α Centauri AB we find that the outer stability limit can be much less than half the Hill Radius due to oscillations in the planetary orbital eccentricity caused by the gravitational interaction with the binary star. We show, furthermore, how the resulting truncation of the outer stability limit can affect the outward tidal migration and potential observability of exomoons through transit timing variations (TTVs). Typical TTV (RMS) amplitudes induced by exomoons in binary systems are ≲10 min and appear more likely for planets orbiting the less massive stellar component. A GitHub repository (saturnaxis/exomoon-in-binaries) is available to reproduce figures.

Comments: 16 pages, 11 figures, 3 tables; Revised relative to first reviewer report; submitted to Astronomical Journal; "for the GitHub repository, see this this https URL"

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Cite as: arXiv:2105.00034 [astro-ph.EP] (or arXiv:2105.00034v1 [astro-ph.EP] for this version)

Submission history

From: Billy Quarles

[v1] Fri, 30 Apr 2021 18:26:10 UTC (14,382 KB)

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