Transit Detectability of Ring Systems around Extrasolar Giant Planets

Abstract

We investigate whether rings around extrasolar planets could be detected from those planets' transit light curves. To this end, we develop a basic theoretical framework for calculating and interpreting the light curves of ringed planet transits on the basis of the existing framework used for stellar occultations, a technique that has been effective for discovering and probing ring systems in the solar system. We find that the detectability of large Saturn-like ring systems is largest during ingress and egress and that a reasonable photometric precision of $(1 3) ; 10 À4 with 15 minute time resolution should be sufficient to discover such ring systems. For some ring particle sizes, diffraction around individual particles leads to a detectable level of forward-scattering that can be used to measure modal ring particle diameters. An initial census of large ring systems can be carried out using high-precision follow-up observations of detected transits and by the upcoming NASA Kepler mission. The distribution of ring systems as a function of stellar age and as a function of planetary semimajor axis will provide empirical evidence to help constrain how rings form and how long rings last. Subject headingg s: occultations-planets: rings-planets and satellites: individual (HD 209458b)-techniques: photometric