Theoretical RV curves for a neutron-star mass m_ns = 1.83   M_⊙ for β₀ = 0.614 (continuous curve; case 65c) and m_ns = 1.468   M_⊙ for β₀ = 0.300 (dash curve; case 61b). Data points are the RV measurements from Barziv et al. (2001): the average of several lines (triangles) and the values for Hδ (crosses). The vertical dash lines indicate the phase of X-ray eclipse, the approximate location of the blue “dip” in the RV curve and the “blue excursion”. The latter may be due to outflows from the B-supergiant. We suggest these outflows may be associated with activity induced by the tidal flows.