Radial velocity curve of the secondary star at decline. The value of |$K_2$| obtained is |$180.0 \pm 3.3$| km s|$^{-1}$|⁠, with a goodness of fit |$\chi ^2 = 318.5$| with 39 deg of freedom and standard deviation |$\sigma =2.86$|⁠. We also observe that the data move further away from the circular fit compared to the data in Fig. 3 (see the text).