Runaway stars from young star clusters containing initial binaries. II - A mass spectrum and a binary energy spectrum

N-body simulations of open star clusters containing initial binaries and supplemental binary-binary scattering experiments have been performed in order to study the production of dynamically ejected runaway stars. These simulations differ from those presented in Paper I (Leonard and Duncan 1988) in that they consider clusters with a mass spectrum and a binary energy spectrum. It has been found that dynamically ejected runaways have a maximum velocity of ≳200 km s-1, a binary frequency of ≃10%, and a mass-velocity relation in which the lowest mass stars have the highest velocities. All three of these properties are consistent with those of the Gies and Bolton Astrophys. J. Suppl. 61, 419 (1986) sample of OB runaway stars. Also, the mass ratios and eccentricities of dynamically ejected binaries are consistent with those of known runaway binaries. Finally, there are enough young star clusters in the Galactic disk to account for the observed number of OB runaways. In conclusion, the dynamical ejection hypothesis appears to be a viable explanation for the OB runaway stars.