  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 non-vanishing 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-T
dwarf stars by planets with sizes ranging from the one of Earth to two 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. Departs from symmetry around mid-transit
in the time dependence of the polarization signature may provide an estimate of
the orbital eccentricity.
