Presentation #417.04 in the session “Extrasolar Planets: Direct Imaging 1”.
Spiral arms have been discovered around more than a dozen of protoplanetary disks, and their formation mechanisms have been under debate. Two leading formation mechanisms, companion-disk interaction and gravitational instability induction, predict distinct motion patterns. By monitoring these systems with multi-epochs observations, here we characterize the motion pattern for the spirals around MWC 758 and SAO 206462: we can not only distinguish the formation mechanism for the spiral systems, but also trace the orbits for these spiral-arm-driving planets. These predicted drivers are ideal for targeted deep high-contrast imaging efforts using Keck and the James Webb Space Telescope.