2005ApJ...635..570C

We investigate the linear polarization in the light of extrasolar planetary systems that may arise as a result of an occultation of the star by a transiting planet. Such an occultation breaks any spherical symmetry over the projected stellar disk and thus results in a nonvanishing linear polarization. This polarization will furthermore vary as the occultation progresses. We present both analytical and numerical results for the occultation of G, K, M, and T dwarf stars by planets with sizes ranging from that of Earth to 2 times the size of Jupiter. We find that the occultation polarization may result in an observable signal and provide additional means to characterize various parameters of the system. A particularly interesting result is that, for the later spectral types (i.e., smaller stellar radii), this polarization signature may be observable even for Earth-like planets. This suggests polarization as a possible tool to detect such planets. Departures from symmetry around midtransit in the time dependence of the polarization signature may provide an estimate of the orbital eccentricity.