2009ApJ...690....1O

We present theoretical predictions for the photometric and spectroscopic signatures of rings around transiting extrasolar planets. On the basis of a general formulation for the transiting signature in the stellar light curve and the velocity anomaly due to the Rossiter effect, we compute the expected signals analytically for a face-on ring system, and numerically for more general configurations. We study the detectability of a ring around a transiting planet located at a = 3 AU for a variety of obliquity and azimuthal angles, and find that it is possible to detect the ring signature both photometrically and spectroscopically unless the ring is almost edge-on (i.e., the obliquity angle, θ, of the ring is much less than unity). We also consider the detectability of planetary rings around a close-in planet, HD 209458b (θ ~ 90° - i_orbit~ 3°.32), and Saturn (θ ~ 26°.7) as illustrative examples. While the former is difficult to detect with the current precision (photometric precision of 10^–4 and radial velocity precision of 1 m/s), a marginal detection of the latter is possible photometrically. If the future precision of the radial velocity measurement goes below 0.1 m/s, they will even be detectable from ground-based spectroscopic observations.