Normalised ${\widehat{\chi }}^2$ measurements for the RV semi-amplitudes K_B of the narrow-lined stripped star (left) and K_Be of the broad-lined Be companion (right). Values of χ² were determined with the shift-and-add disentangling technique from the Balmer Hδ and Hγ, and the He I λ4026, 4144, 4388 and 4472 Å lines. Since the disentangling procedure is non-linear and introduces unrecognised sources of error, we opted to normalise the derived χ² values by multiplication with a scaling factor such that the root mean squared error near the minimum is of order unity. Parabolic fits around the minimum yield best-fitting semi-amplitudes of K_B ≃ 76 ± 0.9 km/s and K_Be ≃ 5 ± 4 km/s, indicated by vertical dashed lines and shaded regions. 1 − σ uncertainties were determined as the intervals ${\widehat{\chi }}^2-{\widehat{\chi }}_{\min }^2\le 1$.