Radial velocity of the receding component vs. RV of the approaching component. Here the black dots refer to pure-sky fibers from the HR15N setup, blue dots to pure-sky from the HR14A setup, and gray dots to sky lines from faint stars. The orange circles represent the average RV of low-mass cluster stars. The dashed line is the expected locus for purely spherical expansion. A subsample of apparently peculiar datapoints is highlighted using “+” symbols.