Observed and disentangled spectra close to quadrature. Observed TRES spectra with orbital phases ϕ = 0.83 (top) and ϕ = 0.17 (bottom) are shown as black solid lines. The disentangled spectral components of the narrow-lined stripped star (dark blue) and the Be star (orange) are shown, Doppler-shifted by the inferred RVs (noted on the right). The observed spectra are well reproduced by the sum of both components (green) but are dominated by the contribution of the narrow-lined stripped star. With a flux contribution of ≈40% (see Sect. 6.1.2) and rotationally broadened absorption lines, the Be star’s contribution to the combined spectrum is barely visible, even though it is the considerably more massive star.