Spectroscopic Binaries in the Orion Nebula Cluster

A search was made for spectroscopic binaries among the 26 brightest members of this very young cluster. Orbital elements are given for four binaries (three known binaries, one newly discovered), and one star is a probable binary. In agreement with published predictions from n-body simulations for binary formation by capture, it is found that the spectroscopic binaries have long periods (median of 20 days), have low-mass companions, are not rotating synchronously with their orbital motions even for a period of 6.5 days, and are probably not concentrated toward the cluster center more than are the massive single stars. The binary frequency is probably normal for a cluster with a high mean rotational velocity.