Two-body model for the system A2440A/A2440(B+C). The horizontal lines show the mass estimate (full line) and errors (dashed lines) (see Sect. 5.5.1). The projected distance of 0.6 Mpc and the radial velocity difference at rest of 730 km s^-1 were derived from the position and velocity of the two centroids. The two systems are assumed to have been at zero separation 12.2 Gyr ago. The dotted line represents the Newtonian criterion for gravitational binding. Two bound incoming (BIa and BIb) and one unbound outgoing (UO) solutions are found compatible with the mass estimates.