Stellar Radial Velocities in the Old Open Cluster M67 (NGC 2682). II.
  The Spectroscopic Binary Population
  We present and analyse 120 spectroscopic binary and triple cluster members of
the old (4 Gyr) open cluster M67 (NGC 2682). 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 45
years, 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 to
0.7 Msolar), from the giants down to ~4 mag below the main-sequence turnoff,
and extends in radius to 30 arcminutes (7.4 pc at a distance of 850 pc, 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. We
derive a tidal circularization period of P_circ = 11.0 +1.1 -1.0 days. We also
analyze the incompleteness-corrected distributions of binary orbital elements
and masses. The period distribution rises toward longer periods. The
eccentricity distribution, beyond P_circ, is consistent with a uniform
distribution. The mass-ratio distribution is also consistent with a uniform
distribution. Overall, these M67 binaries are closely consistent with similar
binaries in the galactic field, as well as the old (7 Gyr) open cluster NGC
188.
  WIYN Open Cluster Study. 83.
