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Description
The open cluster NGC 6791 has been the focus of much recent study due to its intriguing combination of old age and high metallicity (~8Gyr, [Fe/H]=+0.30), as well as its location within the Kepler field. As part of the WIYN Open Cluster Study, we present precise ({sigma}=0.38km/s) radial velocities for proper motion candidate members of NGC 6791 from Platais et al. Our survey, extending down to g' ~ 16.8, is comprised of the evolved cluster population, including blue stragglers, giants, and horizontal branch stars. Of the 280 proper-motion-selected stars above our magnitude limit, 93% have at least one radial velocity measurement and 79% have three measurements over the course of at least 200 days, sufficient for secure radial-velocity-determined membership of non-velocity-variable stars. The Platais et al. proper motion catalog includes 12 anomalous horizontal branch candidates blueward of the red clump, of which we find only 4 to be cluster members. Three fall slightly blueward of the red clump and the fourth is consistent with being a blue straggler. The cleaned color-magnitude diagram shows a richly populated red giant branch and a blue straggler population. Half of the blue stragglers are in binaries. From our radial velocity measurement distribution, we find the cluster's radial velocity dispersion to be {sigma}_c_=0.62+/-0.10km/s. This corresponds to a dynamical mass of ~4600M_{sun}_.
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