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arXiv · 1011.5138

Evidence for Extended Star Formation in the Old, Metal-Rich Open Cluster, NGC 6791?

Bruce A. Twarog·Giovanni Carraro·Barbara J. Anthony-Twarog
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Abstract

NGC 6791 is an old, metal-rich star cluster normally considered to be a disk open cluster. Its red giant branch is broad in color yet, to date, there is no evidence for a metallicity spread among its stars. The turnoff region of the main sequence is also wider than expected from broad-band photometric errors. Analysis of the color-magnitude diagram reveals a color gradient between the core of the cluster and its periphery; we evaluate the potential explanations for this trend. While binarity and photometric errors appear unlikely, reddening variations across the face of the cluster cannot be excluded. We argue that a viable alternative explanation for this color trend is an age spread resulting from a protracted formation time for the cluster; the stars of the inner region of NGC 6791 appear to be older by ~1 Gyr on average than those of the outer region.

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Bruce A. Twarog, Giovanni Carraro, Barbara J. Anthony-Twarog. 2010-11-23. Evidence for Extended Star Formation in the Old, Metal-Rich Open Cluster, NGC 6791?. https://doi.org/10.1088/2041-8205%2F727%2F1%2Fl7

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