Radio and near-infrared observations have observed dozens of protoplanetary
disks that host spiral arm features. Numerical simulations have shown that
companions may excite spiral density waves in protoplanetary disks via
companion-disk interaction. However, the lack of direct observational evidence
for spiral-driving companions poses challenges to current theories of
companion-disk interaction. Here we report multi-epoch observations of the
binary system HD 100453 with the Spectro-Polarimetric High-contrast Exoplanet
REsearch (SPHERE) facility at the Very Large Telescope. By recovering the
spiral features via robustly removing starlight contamination, we measure
spiral motion across 4 yr to perform dynamical motion analyses. The spiral
pattern motion is consistent with the orbital motion of the eccentric
companion. With this first observational evidence of a companion driving a
spiral arm among protoplanetary disks, we directly and dynamically confirm the
long-standing theory on the origin of spiral features in protoplanetary disks.
With the pattern motion of companion-driven spirals being independent of
companion mass, here we establish a feasible way of searching for hidden
spiral-arm-driving planets that are beyond the detection of existing
ground-based high-contrast imagers.Comment: Accepted for publication in Astronomy and Astrophysics; 12 pages, 9
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