WIYN Open Cluster Study. LIX. Radial Velocity Membership of the Evolved Population of the Old Open Cluster NGC 6791

Type Journal Article
Names Benjamin M. Tofflemire, Natalie M. Gosnell, Robert D. Mathieu, Imants Platais
Publication The Astronomical Journal
Volume 148
Issue 4
Pages 61
Journal Abbreviation The Astronomical Journal
Date October 1, 2014
DOI 10.1088/0004-6256/148/4/61
ISSN 0004-6256
URL http://adsabs.org/2014AJ.148.61T
Library Catalog adslabs.org
Abstract 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), as well as its location within the Kepler field. As part of the WIYN Open Cluster Study, we present precise (σ = 0.38 km s-1) 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 σ c = 0.62 ± 0.10 km s-1. This corresponds to a dynamical mass of ~4600 M ⊙.
Tags blue stragglers, open clusters and associations: individual: NGC 6791
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