Bottom of the Balmer lines Hα and Hβ for observations corresponding to a configuration where the difference in RVs is large (top) and small (bottom). The red and blue lines mark the radial velocities of the D and S components, measured on the Ca  II K narrow absorption features, plotted in purple as references. Those RV are − 14.80 ± 0.50 (D), + 15.16 ± 1.54 km s⁻¹ (S) (top), and + 2.75 ± 0.73 (D), − 7.72 ± 1.38 (S) km s⁻¹ (bottom). The dashed line marks the RV of the system, − 2.18 ± 0.32 km s⁻¹. The two green crosses mark the position of telluric lines.