The chemical abundances of open clusters: NGC 752, NGC 1817, NGC 2360 and NGC 2506

Arumalla B. S. Reddy1*, Sunetra Giridhar1 and David L. Lambert2
1Indian Institute of Astrophysics, Bengaluru 560 034, India
2W.J. McDonald Observatory, The University of Texas at Austin, Austin, TX 78712-0259, USA

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Since the Galactic Open Clusters (OCs) provide a sample of stars homogeneous in age and chemical composition and their distances are well determined, they were recognized as suitable candidates to study the chemical evolution of Galaxy. We have analyzed high-dispersion echelle spectra (R≥50,000) of 3-4 red giant members for each open cluster to derive abundances for a whole range of elements including light as well as heavy elements. The membership to the cluster has been confirmed through their radial velocities and proper motions. The spread in temperatures and gravities being very small, nearly the same stellar lines were employed thereby reducing the random errors. Most of these clusters are located in Galactic anti-center direction and we found [Fe/H] values of - 0.02±0.05 for NGC 752, -0.07±0.06 for NGC 2360, -0.11±0.05 for NGC 1817 and -0.19±0.06 for NGC 2506. Abundances relative to Fe for elements from Na to Eu are equal within measurement uncertainties to published abundances for thin disk giants in the field with the possible exception of mild anomalies for Mn, Cu, Ba, Ce and Nd. This supports the view that field stars come from disrupted open clusters.

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Keywords : Galaxy: abundances – stars: abundances