vbyCaHbeta CCD Photometry of Clusters. VIII. The Super-Metal Rich, Old Open Cluster NGC 6791

Abstract

CCD photometry on the intermediate-band vbyCaHbeta system is presented for the metal-rich, old open cluster, NGC 6791. Preliminary analysis led to [Fe/H] above +0.4 with an anomalously high reddening and an age below 5 Gyr. A revised calibration between (b-y)_0 and [Fe/H] at a given temperature shows that the traditional color-metallicity relations underestimate the color of the turnoff stars at high metallicity. With the revised relation, the metallicity from hk and the reddening for NGC 6791 become [Fe/H] = +0.45 +/- 0.04 and E(b-y) = 0.113 +/- 0.012 or E(B-V) = 0.155 +/- 0.016. Using the same technique, reanalysis of the photometry for NGC 6253 produces [Fe/H] = +0.58 +/-0.04 and E(b-y) = 0.120 +/- 0.018 or E(B-V) = 0.160 +/- 0.025. The errors quoted include both the internal and external errors. For NGC 6791, the metallicity from m_1 is a factor of two below that from hk, a result that may be coupled to the consistently low metal abundance from DDO photometry of the cluster and the C-deficiency found from high dispersion spectroscopy. E(B-V) is the same value predicted from Galactic reddening maps. With E(B-V) = 0.15 and [Fe/H] = +0.45, the available isochrones predict an age of 7.0 +/- 1.0 Gyr and an apparent modulus of (m-M) = 13.60 +/- 0.15, with the dominant source of the uncertainty arising from inconsistencies among the isochrones. The reanalysis of NGC 6253 with the revised lower reddening confirms that on both the hk and m_1 metallicity scales, NGC 6253, while less than half the age of NGC 6791, remains at least as metal-rich as NGC 6791, if not richer.

Accepted for Astronomical Journal. 42 p. latex file includes 11 figures and 3 tables, one of which is a short version of a data table to appear in online AJ in its entirety

References in corpus (2)

• High resolution infrared spectroscopy of the old open cluster NGC6791
• uvbyCa H beta CCD Photometry of Clusters. VII. The Intermediate-Age Anticenter Cluster Melotte 71

Cited by in corpus (13)

• The chemical abundance of the very metal rich old Open Clusters NGC 6253 and NGC 6791
• A new standard: Age and distance for the open cluster NGC 6791 from the eclipsing binary member V20
• OCCASO II. Physical parameters and Fe abundances of Red Clump stars in 18 Open Clusters
• A uvbyCaHbeta Analysis of the Old Open Cluster, NGC 6819
• The Helium Abundance of NGC 6791 from Modeling of Stellar Oscillations
• The Old, Super-Metal-Rich Open Cluster, NGC 6791 - Elemental Abundances in Turn-off Stars from Keck/HIRES Spectra
• Asteroseismic Study on Cluster Distance Moduli for RGB Stars in NGC 6791 and NGC 6819
• On the Color-Metallicity Relation of the Red Clump and the Reddening Toward the Magellanic Clouds
• Comparison of the Asteroseismic Mass Scale of Red Clump Giants with Photometric Mass Estimates
• The innermost globular clusters of M87
• The uvbyHbeta Metallicity Calibration for G and K Dwarfs
• Study of the Open Clusters in Kepler Prime Field
• New age-metallicity diagnostic diagram for the Washington photometric system