The detectability of habitable exomoons with Kepler

In this paper, the detectability of habitable exomoons orbiting around giant planets in M-dwarf systems using transit timing variations (TTVs) and transit duration variations (TDVs) with Kepler-class photometry is investigated. Light curves of systems with various configurations were simulated around M-dwarf hosts of mass 0.5 M_⊙ and radius 0.55 R_⊙. Jupiter-like giant planets which offer the best potential for hosting habitable exomoons were considered with rocky super-Earth-mass moons. The detectability is measured by using the phase-correlation between TTV and TDV signals. Since the TDV signal is typically weaker than the TTV signal, confirmation of an exomoon detection will depend on being able to detect a TDV signal. We find that exomoons around planets orbiting within the habitable zone of an M-dwarf host star can produce both detectable TTV and TDV signatures with Kepler-class photometry. While aliasing between the planet period and moon period may hinder exomoon detection, we also find some strong correlation signatures in our simulation (e.g. correlation: >0.7) which would provide convincing exomoon signatures. With the addition of red noise stellar variability, correlations generally weaken. However simulated examples with planet masses less than around 25 M_⊕, moons of mass 8-10 M_⊕ and specific values of planet and moon periods still yield detectable correlation in 25-50 per cent of cases. Our simulation indicates that Kepler provides one of the best available opportunities for exomoon detection.