System (center of mass) velocity as a function of the mass of source I (see also Fig. 1). Red lines show the scenario where source x is part of the ejection event, as suggested by Luhman et al. (2017)¹. The red shaded area shows the result of varying the mass of source x between 2.5–3.0 M_⊙, and the black arrows show the direction of the increment. Blue lines show the scenario in which source x is not part of the event. In the red and blue cases, the dashed and dot-dashed lines show results of adopting the lower and upper limits on the mass of BN, respectively (Rodríguez et al. 2005).