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C.L. Slesnick (Dept of Phys and Astronomy, NAU, and Dept of Phys, NYU), P. Massey (Kitt Peak National Observatory, NOAO, and Dept Phys and Astronomy, NAU)
Some of the most fundamental questions one can ask about star clusters include: Do all the stars form at the same time? Is the formation time dependent on mass? Despite the importance of these questions, answers to them have been inconclusive. The Double Cluster h and Chi Persei (NGC 869 and NGC 884, respectively) is one of the closest, brightest clusters to us. On a clear night, one can even see it with a naked eye!
In this study we investigate the stellar content of the Double Cluster, and determine the ages of its member stars. Mosaic CCD imaging has been taken in a 1 deg2 field around the cluster resulting in new photometry of 4527 stars. Spectroscopy data has been collected using a variety of instruments including the multiobject, fiber positioner Hydra and the Coude Feed. From this data we have obtained new spectral classifications of 220 stars. The reddening and distance modulus of h and Chi Per have been redetermined utilizing these data and used to determine new H-R diagrams.
Before this study the only deep investigation of the Double Cluster was that of Wildey (1964) who used photographic plates and photoelectric techniques. From his data he constructed an H-R diagram which implied the stars were formed during three distinct epochs. Though our results are not final, we see remarkable similarities between the two diagrams; most differences will be due to improvements in stellar evolution models that have come about in the past 35 years.
CLS's participation in this project was made possible through the Research Experiences for Undergrates Program, which was supported by the National Science Foundation under Grant No. 9423921 to Northern Arizona University.
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