Gravitational microlensing of stars with transiting planets

Abstract

If planetary systems are ubiquitous then a fraction of stars should possess a transiting planet when being microlensed. This paper presents a study of the influence of such planets on microlensing light curves. For the giant planets recently identified, the deviations in the light curve can be substantial, although the specifics of the perturbations are dependent upon the radius of the planet relative to that of the star, the location of the planet over the stellar surface and the orientation of the sweeping caustic. Given that the instantaneous probability of transiting hot-Jupiter like planets is small, less than a percent, and only a proportion of microlensing events exhibit caustic crossing events, the probability of detecting a transiting planet during a microlensing event is small, $\sim10^{-6}$. However, a number of factors influencing this probability, such as the number of solar type star that possess planets, are uncertain, and the prospect of detecting transiting planets in future large catalogues of microlensing light curves may be viable. The results of this study also have bearing on the gravitational microlensing of spots on the stellar surface.