Photometric membership and metallicities of red giant candidates in selected open clusters

Jean-Claude Mermilliod
2008
Journal paper

Abstract

As part of a long-term project to determine abundances and astrophysical properties of evolved red stars in open clusters, we present high-precision DDO photoelectric observations for a sample of 33 red giant candidates projected in the fields of nine Galactic open clusters. These data are supplemented with UBV photoelectric photometry of 24 of these stars as well as with CORAVEL radial-velocity observations for 13 red giant candidates in four of the clusters. We also present Washington photoelectric photometry of a small sample of red giant candidates of the open cluster Ruprecht 97. The likelihood of cluster membership for each star photometrically observed and for 23 additional red giant candidates with UBV and DDO data available in the literature, is evaluated by using two independent photometric criteria. Nearly 82% of the analysed stars are found to have a high probability of being cluster giants. Photometric membership probabilities show very good agreement with those obtained from CORAVEL radial velocities. While E(B - V) colour excesses were determined from combined B - V and DDO colours, calibrations of the DDO system were used to derive MK spectral types, effective temperatures and metallicities.The derived DDO metallicities range between values typical of moderately metal-poor clusters ([Fe/H] = -0.19) to moderately metal-rich ([Fe/H] = 0.25) ones. (c) 2009 WILEY-VCH Verla, GmbH&Co. KGaA, Weinheim.

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