Doppler velocities at different orbital phases of Si IX (circles), Si VIII (squares), Si VII (diamonds), and Si VI (upside down triangles), from Schulz et al. (2002, S02, blue) and Goldstein et al. (2004, G04, orange), as adjusted for laboratory reference values by Hell et al. (2016), from Grinberg et al. (2017, G17, green), and from the present work (RA, red). The solid and dashed lines stand for the radial velocities of the NS and the giant star, respectively.