luna: an algorithm for generating dynamic planet-moon transits

• Published in: Monthly notices of the Royal Astronomical Society Vol. 416; no. 1; pp. 689 - 709
• Main Author: Kipping, David M.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.09.2011; Wiley-Blackwell; Oxford University Press
• Subjects: Astronomy; Earth, ocean, space; eclipses; Exact sciences and technology; Extrasolar planets; methods: analytical; Moons; planetary systems; Planetology; planets and satellites: general; techniques: photometric; methods: analytical; planetary systems; eclipses; planets and satellites: general; techniques: photometric; Extrasolar planets; Light curves; Planetary system; Habitable space; Algorithms; Asymmetry; Neptune planet; Limb darkening; Dynamics; Analytical method; Timing; Photometry
• ISSN: 0035-8711; 1365-8711; 1365-2966; 1365-2966
• DOI: 10.1111/j.1365-2966.2011.19086.x

It has been previously shown that moons of extrasolar planets may be detectable with the Kepler Mission, for moon masses above ∼0.2 M⊕. Transit timing effects have been formerly identified as a potent tool to this end, exploiting the dynamics of the system. In this work, we explore the simulation of transit light curves of a planet plus a single moon including not only the transit timing effects, but also the light-curve signal of the moon itself. We introduce our new algorithm, luna, which produces transit light curves for both bodies, analytically accounting for shadow overlaps, stellar limb darkening and planet-moon dynamical motion. By building the dynamics into the core of luna, the routine automatically accounts for transit-timing/duration variations and ingress/egress asymmetries for not only the planet, but also the moon. We then generate some artificial data for two feasibly detectable hypothetical systems of interest: (i) prograde and (ii) retrograde Earth-like moons around a habitable-zone Neptune for an M dwarf system. We fit the hypothetical systems using luna and demonstrate the feasibility of detecting these cases with Kepler photometry.