WASHINGTON PHOTOMETRY OF NEARBY F-DWARF, G-DWARF, AND K-DWARF

We present Washington C, M, T1, T2, and Johnson V, B-V photometry of nearby F, G, and K dwarfs. Our calibrations of [Fe/H] with the Washington colors have residuals approaching those of spectroscopic metallicities. The color-magnitude calibrations are based on nearby stars having precise parallaxes with metallicities ranging from 0.25 to -1.8 dex relative to the Sun. We conclude that the C-M and M - T2 colors are the best ones for determining metallicities in dwarfs using the Washington photometric system; the T1 filter would be redundant to the M filter. Our study is a preliminary one and slight refinements from additional observations would allow our calibrations to replace the Hyades as the lowest rung in the distance ladder.