We present results from 13776 radial-velocity measurements of 1278 candidate members of the old ( 4 Gyr ) open cluster M67 ( NGC 2682 ) .
The measurements are the results of a long-term survey that includes data from seven telescopes with observations for some stars spanning over 40 years .
For narrow-lined stars , radial velocities are measured with precisions ranging from about 0.1 to 0.8 km s ^ { -1 } .
The combined stellar sample reaches from the brightest giants in the cluster down to about 4 magnitudes below the main-sequence turnoff ( V = 16.5 ) , covering a mass range of about 1.34 M _ { \odot } to 0.76 M _ { \odot } .
Spatially , the sample extends to a radus of 30 arcminutes ( 7.4 pc in projection at a distant of 850 pc or 6-7 core radii ) .
We find M67 to have a mean radial velocity of +33.64 km s ^ { -1 } ( with an internal precision of \pm 0.03 km s ^ { -1 } ) well separated from the mean velocity of the field .
For stars with \geq 3 measurements , we derive radial-velocity membership probabilities and identify radial-velocity variables , finding 562 cluster members , 142 of which show significant radial-velocity variability .
We use these cluster members to construct a color-magnitude diagram and identify a rich sample of stars that lie far from the standard single star isochrone , including the well-known blue stragglers , sub-subgiants and yellow giants .
These exotic stars have a binary frequency of ( at least ) 80 % , more than three times that detected for stars in the remainder of the sample .
We confirm that the cluster is mass segregated , finding the binaries to be more centrally concentrated than the single stars in our sample at the 99.8 % confidence level ( and at the 98.7 % confidence level when only considering main-sequence stars ) .
The blue stragglers are centrally concentrated as compared to the solar-type main-sequence single stars in the cluster at the 99.7 % confidence level .
Accounting for measurement precision , we derive a radial-velocity dispersion in M67 of 0.80 \pm 0.04 km s ^ { -1 } for our sample of single main-sequence stars , subgiants and giants with V \leq 15.5 .
When corrected for undetected binaries , this sample yields a true radial-velocity dispersion of 0.59 \substack { +0.07 \ -0.06 } km s ^ { -1 } .
The radial distribution of the velocity dispersion is consistent with an isothermal distribution within our stellar sample .
Using the cluster radial-velocity dispersion , we estimate a virial mass for the cluster of 2100 \substack { +610 \ -550 } M _ { \odot } .