Radial Velocities of binary population in M67

As a cornerstone of stellar astrophysics, M67 is a key cluster in the WIYN Open Cluster Study (WOCS); radial-velocity (RV) observations of M67 are ongoing and extend back over 45yr, incorporating data from seven different telescopes, and allowing us to detect binaries with orbital periods <~10^4^days.

Our sample contains 1296 stars (604 cluster members) with magnitudes of 10<~V<~16.5 (about 1.3-0.7M{sun}), from the giants down to ~4mag below the main-sequence turnoff, and extends in radius to 30' (7.4pc at a distance of 850pc, or ~7 core radii). This paper focuses primarily on the main-sequence binaries, but orbital solutions are also presented for red giants, yellow giants, and sub-subgiants. Out to our period detection limit and within our magnitude and spatial domain, we find a global main-sequence incompleteness-corrected binary fraction of 34%{+/-}3%, which rises to 70%{+/-}17% in the cluster center.