Top panel: AAVSO visual light curve (gray crosses). Black squares correspond to TiO-band temperatures derived from the HERMES spectra in Sect. 3.4. Gray shaded areas in all panels define four photometric cycles, three of those being represented as hysteresis loops in Fig. 2. Second panel from the top: radial velocities (RVs) in all masks derived from fitting Betelgeuse cross-correlation functions (CCFs) with single- or multi-component Gaussian functions. RVs from the main CCF component are connected with lines. Line-doubling events are shown with a star symbol. The different colors correspond to the different masks defined in Table A.1. The same color coding is applied in the second to fifth panels. The zero point of the velocity scale corresponds to Betelgeuse center-of-mass velocity, represented by a horizontal dashed line. The uncertainty on HERMES individual RVs is on the order of 0.1 km s⁻¹. Third panel:M₁ velocities (see definition in Sect. 3.2) of CCFs in masks C2–C5. Fourth panel: atmospheric velocity gradients between masks C5 and C2 (orange), C5 and C3 (green), and C5 and C4 (blue). Bottom panel: the FWHM of CCFs in masks C2–C5.