Transit Detectability of Ring Systems around Extrasolar Giant Planets

We investigate whether rings around extrasolar planets could be detected fromthose planets' transit lightcurves. To this end we develop a basic theoreticalframework for calculating and interpreting the lightcurves of ringed planettransits based on the existing framework used for stellar occultations, atechnique which has been effective for discovering and probing ring systems inthe solar system. We find that the detectability of large, Saturn-like ringsystems is largest during ingress and egress, and that reasonable photometricprecisions of $\sim 1-3 \times 10^{-4}$ with 15-minute time resolution shouldbe sufficient to discover such ring systems. For some ring particle sizes,diffraction around individual particles leads to a detectable level offorward-scattering that can be used to measure modal ring particle diameters.An initial census of large ring systems can be carried out using high-precisionfollow-up observations of detected transits and by the upcoming NASA\emph{Kepler} mission. The distribution of ring systems as a function ofstellar age and as a function of planetary semimajor axis will provideempirical evidence to help constrain how rings form and how long rings last.Comment: 13 pages, to appear in the 2004 December 1 Astrophysical Journa