WIYN Open Cluster Study: The Next Generation

Abstract

We summarize the present status and discuss future directions of the WIYN Open Cluster Study (WOCS). The goals of the WOCS collaboration are 1) to establish a multidimensional database of properties for stars in selected open clusters, including photometric (colors, magnitudes, magnitude variations), astrometric (positions, proper motions), and spectroscopic (chemical abundances, radial velocities) characteristics, and 2) to investigate a broad set of astrophysical questions through the study of open clusters. In the area of astrometry, WOCS has underway an ambitious program to combine existing 4-m plate collections with newly acquired images from large-format CCD mosaics. This effort will continue into the next decade as we complete propermotion studies of northern and southern open clusters while at the same time expanding the temporal baseline over which astrometric studies of these clusters are performed. The WOCS photometric effort is currently focused in the optical (UBVRI) regime; we plan to extend the photometry to the infrared (JHK) passbands. Optical and infrared photometry of comparable depth and precision will facilitate a number of scientific investigations that are currently not possible. The WOCS radial-velocity program has obtained several thousand radial-velocity measurements of samples containing hundreds of stars in each of four open clusters. The number of clusters being surveyed will grow, and with an increase of a factor of a few in precision the project will expand into the detection of brown dwarf and large planet companions. Finally, WOCS is committed to improving the accuracy of metallicity determinations in fundamental clusters by a factor of a few through careful control of systematic errors. These abundance analyses also include lithium, which will prove an ideal probe of diffusion, mixing, mass loss, and other processes in stellar evolution. The WOCS observations have primarily been made with the WIYN 3.5-m and O.9-m telescopes, and we anticipate that these facilities will continue to play the central role for northern WOCS studies.