Linear correlation between the RVs of the components of WDS 10209–5603 Bab. Open squares represent measurements made in February 2013. These are fitted by the function RV_Ba = −0.63RV_Bb + 9.1 km s^-1, which is shown with a long-dashed line. Open triangles represent measurements made in February and April 2008, and filled circles indicate measurements of March and May 2009. Adopting a mass ratio q = 0.63, these data are fitted by the function RV_Ba = −0.63RV_Bb + 20.0 km s^-1 (short-dashed line), and the function RV_Ba = −0.63RV_Bb + 17.0 km s^-1 (dotted line), respectively. Open circle indicates RVs measured in a spectrum acquired in April 2010.