Angular velocity of the S1 spiral pattern motion in HD 100453 (black line). It could follow local Keplerian motion (green curve) or be smaller than the maximum value of the companion orbital motion (blue curve), under gravitational instability (GI) or companion–disk interaction, respectively. The measured spiral motion is consistent with the companion motion in the system and is inconsistent with the local Keplerian motion, revealing the companion-driven origin of the spiral arm S1, while excluding the GI origin. The motions here adopt a central stellar mass of 1.70 ± 0.09 M_⊙. The colored shaded regions around each curve represent the corresponding uncertainties.