Astronomy and Astrophysics – Astrophysics
Scientific paper
2002-03-05
Astronomy and Astrophysics
Astrophysics
12 columns, preprint format; 9 figures, gzipped compressed postscript; accepted for May 2002 Astronomical Journal
Scientific paper
10.1086/340075
Analysis of cluster and field star uvby data demonstrates the existence of a previously undetected discrepancy in a widely used photometric metallicity calibration for G dwarfs. The discrepancy is systematic and strongly color-dependent, reducing the estimated [Fe/H] for stars above [Fe/H] ~ -0.2 by between +0.1 and +0.4 dex, and creating a deficit of metal-rich stars among dwarfs of mid-G and later spectral type. The source of the problem, triggered for stars with b-y greater than about 0.47, appears to be an enhanced metallicity dependence for the c1 index that increases as temperature declines. The link between c1, normally a surface gravity indicator, and metallicity produces two secondary effects. The deficit in the photometric abundance for a cool dwarf is partially compensated by some degree of evolution off the main sequence and cool dwarfs with metallicities significantly above the Hyades are found to have c1 indices that classify them as giants. The potential impact of the problem on stellar population studies is discussed.
Anthony-Twarog Barbara J.
Tanner Delora
Twarog Bruce A.
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