Probing Planets with Exomoons: The Cases of Kepler-1708 b and Kepler-1625 b

Abstract

The tidal interactions between a planet and moon can provide insight into the properties of the host planet. The recent exomoon candidates Kepler-1708 b-i and Kepler-1625 b-i are Neptune-sized satellites orbiting Jupiter-like planets and provide an opportunity to apply such methods. We show that if the tidal migration time is roughly equal to the age of these systems, then the tidal dissipation factor Q for the planets Kepler-1708 b and Kepler-1625 b have values of ~$3\times 10^5-3\times 10^6$ and ~$1.5\times 10^5-4\times 10^5$, respectively. In each case, these are consistent with estimates for gas giant planets. Even though some work suggests an especially large semimajor axis for Kepler-1625 b-i, we find that this would imply a surprisingly low Q~2000 for a gas giant unless the moon formed at essentially its current position. More detailed predictions for the moons' initial semimajor axis could provide even better constraints on Q, and we discuss the formation scenarios for a moon in this context. Similar arguments can be used as more exomoons are discovered in the future to constrain exoplanet interior properties. This could be especially useful for exoplanets near the sub-Neptune/super-Earth radius gap where the planet structure is uncertain.

arXiv comment6 pages, 2 figures, submitted for publication in ApJL

References in corpus (26)

• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• HST Time-Series Photometry of the Transiting Planet of HD 209458
• Stability of Satellites Around Close-in Extrasolar Giant Planets
• The Hunt for Exomoons with Kepler (HEK): I. Description of a New Observational Project
• The Physics of Bodily Tides in Terrestrial Planets, and the Appropriate Scales of Dynamical Evolution
• Evidence for a Large Exomoon Orbiting Kepler-1625b
• Challenges in Planet Formation
• Formation, Habitability, and Detection of Extrasolar Moons
• Tidal Friction and Tidal Lagging. Applicability Limitations of a Popular Formula for the Tidal Torque
• HEK VI: On the Dearth of Galilean Analogs in Kepler and the Exomoon Candidate Kepler-1625b I
• On the Terminal Rotation Rates of Giant Planets
• Formation of Giant Planet Satellites
• An Exomoon Survey of 70 Cool Giant Exoplanets and the New Candidate Kepler-1708 b-i
• Outcomes and Duration of Tidal Evolution in a Star-Planet-Moon System
• No Evidence for Lunar Transit in New Analysis of Hubble Space Telescope Observations of the Kepler-1625 System
• Effects of the Planetary Temperature on the Circumplanetary Disk and on the Gap
• The effect of close-in giant planets' evolution on tidal-induced migration of exomoons
• The nature of the giant exomoon candidate Kepler-1625 b-i
• Loose Ends for the Exomoon Candidate Host Kepler-1625b
• Exoplanets Torqued by the Combined Tides of a Moon and Parent Star
• Catching a planet: A tidal capture origin for the exomoon candidate Kepler 1625b I
• Can close-in giant exoplanets preserve detectable moons?
• Exploring formation scenarios for the exomoon candidate Kepler 1625b I
• Application of Orbital Stability and Tidal Migration Constraints for Exomoon Candidates
• Impact of Tides on the Potential for Exoplanets to Host Exomoons
• The Stability of Tidal Equilibrium for Hierarchical Star-Planet-Moon Systems

Cited by in corpus (3)

• Pathways of Survival of Exomoons and Inner Exoplanets
• Tidally Heated Exomoons around $\epsilon$ Eridani b: Observability and prospects for characterization
• The Dynamics of Co-orbital Giant Exomoons -- Applications for the Kepler-1625 b and Kepler-1708 b Satellite Systems