Constraints on mass ejection in black hole formation, derived from black hole X-ray binaries

G. Nelemans, T. M. Tauris, E. P. J. van den Heuvel

Both the recently observed high runaway velocities of Cyg X-1 (~50 km/s) and X-ray Nova Sco 1994 (> ~100 km/s) and the relatively low radial velocities of the black hole X-ray bina…