Predictable patterns in planetary transit timing variations and transit duration variations due to exomoons

Abstract

We present new ways to identify single and multiple moons around extrasolar planets using planetary transit timing variations (TTVs) and transit duration variations (TDVs). For planets with one moon, measurements from successive transits exhibit a hitherto undescribed pattern in the TTV-TDV diagram, originating from the stroboscopic sampling of the planet's orbit around the planet-moon barycenter. This pattern is fully determined and analytically predictable after three consecutive transits. The more measurements become available, the more the TTV-TDV diagram approaches an ellipse. For planets with multiple moons in orbital mean motion resonance (MMR), like the Galilean moons, the pattern is much more complex and addressed numerically in this report. Exomoons in MMR can also form closed, predictable TTV-TDV figures if the drift of the moons' pericenters is sufficiently slow. We find that MMR exomoons produce loops in the TTV-TDV diagram and that the number of these loops is equal to the order of the MMR, or the largest integer in the MMR ratio. We use a Bayesian model and Monte Carlo simulations to test the discoverability of exomoons using TTV-TDV diagrams with current and near-future technology. In a blind test, two of us (BP, DA) successfully retrieved a large moon from simulated TTV-TDV by co-authors MH and RH, which resembled data from a known Kepler planet candidate. Single exomoons with a 10% moon-to-planet mass ratio, like to Pluto-Charon binary, can be detectable in the archival data of the Kepler primary mission. Multi-exomoon systems, however, require either larger telescopes or brighter target stars. Complementary detection methods invoking a moon's own photometric transit or its orbital sampling effect can be used for validation or falsification. A combination of TESS, CHEOPS, and PLATO data would offer a compelling opportunity for exomoon discoveries around bright stars.

published in A&A, text updated to journal version, note added in proofs, 10 Figs. in main text (5 col, 5 b/w), 4 Figs. in appendix (b/w), TTV-TDV simulator available at https://github.com/hippke/TTV-TDV-exomoons

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Cited by in corpus (22)

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• The nature of the giant exomoon candidate Kepler-1625 b-i
• Can close-in giant exoplanets preserve detectable moons?
• On The Feasibility of Exomoon Detection Via Exoplanet Phase Curve Spectral Contrast
• Transits of Inclined Exomoons - Hide and Seek and an Application to Kepler-1625
• Exomoon indicators in high-precision transit light curves
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• Pandora: A fast open-source exomoon transit detection algorithm
• Terminus: A Versatile Simulator for Space-based Telescopes
• The Exomoon Corridor for Multiple Moon Systems
• Astrophysics with New Horizons: Making the Most of a Generational Opportunity
• Tidally Heated Exomoons around $\epsilon$ Eridani b: Observability and prospects for characterization
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• On the Stability of Additional Moons Orbiting Kepler-1625 b
• Signal preservation of exomoon transits during light curve folding
• The Exoplanet Edge: Planets Don't Induce Observable TTVs with a Dominant TTV Period Faster than Half their Orbital Period
• Exploring Exoplanet Dynamics with JWST: Tides, Rotation, Rings, and Moons
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• Search for possible exomoons with FAST telescope
• Fourier series for eclipses on exoplanet binaries