WIYN Open Cluster Study: Radial Velocity Membership of the Evolved Population of Open Cluster NGC 6791
American Astronomical Society, AAS Meeting #222, #214.04
Published in Jun 2013
The open cluster NGC 6791 has been the focus of much recent study due to its intriguing combination of old age and high metallicity 8 Gyr, [Fe/H]=+0.30), and its location within the Kepler field. As part of the WIYN Open Cluster Study (WOCS), we present precise 0.5 km/s) radial velocities for proper-motion candidate members of NGC 6791 from Platais et al. 2011. The WIYN 3.5m telescope and Hydra Multi-Object Spectrograph offer the ideal facility for making definitive cluster membership measurements via radial velocities. Our survey, extending down to 16.5, probes the evolved cluster population, including blue straggler and horizontal branch (HB) candidates. Of the 156 proper-motion selected stars above our magnitude limit, all have at least one radial-velocity measurement and 82% have three measurements, sufficient for secure radial-velocity-determined membership of non-velocity-variables. The Platais et al. 2011 proper-motion catalog includes twelve HB candidates, of which we find only four to be cluster members. Three fall slightly blueward of the red clump and the fourth confirms membership of a blue-HB star from Green and Liebert 1996. This star is also consistent with being a blue straggler. We will include an analysis of the evolved cluster membership and identify radial-velocity-variable objects. Support for this program is provided by NSF grant AST-0908082.
(c) 2013: American Astronomical Society