Left panel: scattered light image of β Pic's large-scale debris disk and of β Pic b (credit: ESO; Lagrange et al. 2009a), with the CO blueshifted disk lobe and the side of the disk facing toward the observer indicated. Middle panel: the orbit of β Pic b (orbital elements from Gravity Collaboration et al. 2020), with the plane of the primary disk and the plane of the warped disk marked as gray and orange lines, respectively. The position of β Pic b at the time of our observations has been marked with blue points. Right panel: photocenter displacements measured in the Brγ line (color points) and in the continuum (gray points). The line channels are colored based on their wavelength, using the same color-coding as Figure 2. Given that the line is in absorption, the photocenters in the redshifting wing of the line are displaced toward the side of photosphere that is approaching the observer (and equivalent for the blueshifted ling wing and the receeding side of the star). The solid black line gives the best-fit position angle for the equatorial plane of the star, with the dashed black lines giving the 1σ error intervals. In all panels, north is top and east is left.