Transiting extrasolar planet with a companion: Effects of orbital eccentricity and inclination

Abstract

Continuing work initiated in an earlier publication (Sato & Asada, 2009, PASJ, 61, L29), 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 the 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 also discuss a narrow region of parameters that produce a mutual transit by an extrasolar satellite. © 2010. Astronomical Society of Japan.