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Dynamics of the Open Cluster NGC 188: A Comparison to an N-body Simulation of M67

Published online by Cambridge University Press:  01 September 2007

Aaron M. Geller ,
Robert D. Mathieu ,
Hugh C. Harris  and
Robert D. McClure
Aaron M. Geller
Affiliation:
Department of Astronomy, University of Wisconsin – Madison, WI, 53706, USA; geller@astro.wisc.edu
Robert D. Mathieu
Affiliation:
Department of Astronomy, University of Wisconsin – Madison, WI, 53706, USA; geller@astro.wisc.edu
Hugh C. Harris
Affiliation:
United States Naval Observatory, Flagstaff, AZ, 86001, USA
Robert D. McClure
Affiliation:
Dominion Astrophysical Observatory, Victoria, B.C., V8X 4M6, Canada
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Abstract

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We present a detailed dynamical study of the old (7 Gyr) open cluster NGC 188. Our combined radial-velocity data set spans a baseline of 35 years, a magnitude range of 12 ≤ V ≤ 16.5, and a 1° diameter region on the sky. Our magnitude limits include solar-mass main-sequence stars, subgiants, giants, and blue stragglers, and our spatial coverage extends radially to 11.5 core radii. We have measured radial velocities for 1014 stars in the direction of NGC 188 with a precision of 0.4 km s−1, and have calculated radial-velocity membership probabilities for stars with ≥ 3 measurements. We find 420 stars to be high-probability cluster members, including 137 spectroscopic binaries. These detectable binaries all have orbital periods of less than 104 days, and thus are hard. We have derived orbit solutions for 67 member binary stars, and use our 35 main-sequence binaries with orbit solutions to compare the eccentricity and period distributions with simulated observations of the Hurley et al. (2005) model of M67 (4.5 Gyr). We also compare the spatial distributions of cluster member populations.

Keywords

Stars: spectroscopic binariesblue stragglersGalaxy: open clusters
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 3 , Symposium S246: Dynamical Evolution of Dense Stellar Systems , September 2007 , pp. 111 - 112
Copyright
Copyright © International Astronomical Union 2008

References

Duquennoy, A. & Mayor, M. 1991, A&A, 248, 485Google Scholar
Hurley, J. R., Pols, O. R., Aarseth, S. J., & Tout, C. A. 2005, MNRAS, 363, 293CrossRefGoogle Scholar