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[14.14] Photometric Study of Old Open Clusters Berkeley 12, Berkeley 17, Berkeley 31, and NGC 188

Z. C. Krusberg, B. Chaboyer (Dartmouth College)

Old open clusters are of great importance in the study of galactic evolution, as these provide a reliable way to determine ages of disk stars. BVI CCD photometry from observations made at the MDM Observatory's 2.4m Hiltner Telescope are presented for the old open clusters Be 12, Be 17, Be 31, and NGC 188. These observations were obtained under photometric conditions and reach well past the main sequence turn-off. Although Berkeley 17 has been long recognized as perhaps the oldest known open cluster, no accurate age determination exists for this important cluster. Cluster ages are determined based on isochrone fits to the color-magnitude diagrams. The well studied cluster NGC 188 was used as the fidicual cluster, and precise relative ages for Be 12, 17 and 31 are derived relative to NGC 188. In addition, radial distributions of cluster member stars are presented and used to establish the angular cluster radii for Be 12, 17, and 31.

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.