On the detection of satellites of extrasolar planets with the method of transits

¹ Institut d'Astrophysique de Paris, 98 bis boulevard Arago, 75014 Paris, France
² DARC, Observatoire de Meudon, Place Jules Janssen, 92195 Meudon, France

Send offprint request to: P. Sartoretti e-mail: sartoret@iap.fr

Received: 27 March 1998
Accepted: 9 September 1998

Abstract

We compute the detection probability of satellites of extrasolar planets with the method of transits, under the assumption that the duration of the observations is at least as long as the planet orbital period. We separate the cases when the parent planet does and does not also transit over the star. The possible satellites are assumed to have orbital radii between the Roche limit and the Hill radius. We find that if a satellite is extended enough to produce a detectable drop in the stellar lightcurve, the probability to detect it when the planet also transits over the star is nearly unity. If the planet does not transit, the probability to detect a Jupiter-like or terrestrial satellite is modest, but it can be comparable to that of detecting a planet if the satellite orbital radius is large. If a satellite is not extended enough to produce a detectable drop in the stellar lightcurve during a transit, it might still be detected through the time shift of planetary transits resulting from the rotation of the planet around the barycenter of the planet-satellite system.