A Multi-ringed, Modestly Inclined Protoplanetary Disk around AA Tau

AA Tau is the archetype for a class of stars with a peculiar periodic photometric variability thought to be related to a warped inner disk structure with a nearly edge-on viewing geometry. We present high resolution (similar to 0.'' 12) ALMA observations of the 0.87 and 1.3 mm dust continuum emission from the disk around AA Tau. These data reveal an evenly spaced three-ringed emission structure, with distinct peaks at 0.'' 34, 0.'' 66, and 0.'' 99, all viewed at a modest inclination of 59.degrees 1 +/- 0.degrees 3 (decidedly not edge-on). In addition to this ringed substructure, we find nonaxisymmetric features, including a bridge of emission that connects opposite sides of the innermost ring. We speculate on the nature of this bridge in light of accompanying observations of HCO+ and (CO)-C-13 (J = 3-2) line emission. The HCO+ emission is bright interior to the innermost dust ring, with a projected velocity field that appears rotated with respect to the resolved disk geometry, indicating the presence of a warp or inward radial flow. We suggest that the continuum bridge and HCO+ line kinematics could originate from gap-crossing accretion streams, which may be responsible for the long-duration dimming of optical light from AA Tau.