Transit Detectability of Ring Systems around Extrasolar Giant Planets

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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 similar to(1-3) x 10(-4) 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.