Transiting Extrasolar Planet with a Companion: Effects of Orbital Eccentricity and Inclination

TL;DR

This paper develops a method to determine the orbital parameters of a moon around a transiting exoplanet using light curve analysis, accounting for eccentricity and inclination effects.

Contribution

It introduces a formulation for extracting orbital elements of a moon from transit light curves, including in small-eccentricity and exact cases, expanding previous work.

Findings

Orbital parameters can be derived from light curves alone.

The method works for small eccentricities and in exact form.

A parameter space for mutual transits by satellites is identified.

Abstract

Continuing work initiated in an earlier publication [Sato and Asada, PASJ, 61, L29 (2009)], we consider light curves influenced by the orbital inclination and eccentricity of a companion in orbit around a transiting extrasolar planet (in a planet-satellite system or a hypothetical true binary). We show that the semimajor axis, eccentricity and inclination angle of a `moon' orbit around the host planet can be determined by transit method alone. For this purpose, we present a formulation for the parameter determinations in a small-eccentricity approximation as well as in the exact form. As a result, the semimajor axis is expressed in terms of observables such as brightness changes, transit durations and intervals in light curves. We discuss also a narrow region of parameters that produce a mutual transit by an extrasolar satellite.