  The young star AB Aurigae is surrounded by a complex combination of gas-rich
and dust dominated structures. The inner disk which has not been studied
previously at sufficient resolution and imaging dynamic range seems to contain
very little gas inside a radius of least 130 astronomical units (AU) from the
star. Using adaptive-optics coronagraphy and polarimetry we have imaged the
dust in an annulus between 43 and 302 AU from the star, a region never seen
before. An azimuthal gap in an annulus of dust at a radius of 102 AU, along
with a clearing at closer radii inside this annulus, suggests the formation of
at least one small body at an orbital distance of about 100 AU. This structure
seems consistent with crude models of mean motion resonances, or accumulation
of material at two of the Lagrange points relative to the putative object and
the star. We also report a low significance detection of a point source in this
outer annulus of dust. This source may be an overdensity in the disk due to
dust accreting onto an unseen companion. An alternate interpretation suggests
that the object's mass is between 5 and 37 times the mass of Jupiter. The
results have implications for circumstellar disk dynamics and planet formation.
