Gas column density of the disk around UX Tau A being gravitationally perturbed by UX Tau C. The orbit of the perturber is in the plane of the sky and the disk is inclined by 40° with PA = 167°, as in the observations. The letters F- and B- label flyby and bound orbit models, respectively. The morphology of the spirals and the current projected distance between the stars suggest that UX Tau C is on an unbound orbit. We note that increasing the outer disk radius for a flyby (as in F90-a100) renders the spirals denser and brighter in scattered light, as they capture more disk material. In each panel, the position (separation, PA) and relative motion (proper motion, relative V_rad) of UX Tau C are compatible with observations. Videos of F90−a100 and B90−e075 are available online.