New metallicity calibration down to [Fe/H] = -2.75 dex

Abstract

88 dwarfs, covering the colour index interval 0.37 <(B-V)o <= 1.07 mag, with metallicities -2.70 <= [Fe/H] <= +0.26 dex have been taken from three different sources for new metallicity calibration. The catalogue of Cayrel de Stroble et al. (2001) which includes 65% of the stars in our sample supplies detailed information on abundances for stars with determination based on high resolution spectroscopy. 77 stars which supplies at least one of the following conditions have been used as &#34;corner stones&#34; for constructing the new calibration: (i) the parallax is larger than 10 mas (distance relative to the Sun less than 100 pc) and the galactic latitude is absolutely higher than 30 degrees, (ii) the parallax is rather large, if the galactic latitude is absolutely low and vice versa. Contrary to the previous investigations, a third-degree polynomial fitted for the new calibration: [Fe/H] = 0.10-2.76d-24.04d^2+30.00d^3. The coefficients were evaluated by the least-square method, without regarding the metallicity of Hyades. However, the constant term is in the range of metallicity determined for this cluster i.e.: 0.08 <= [Fe/H] <= 0.11 dex. The mean deviation and the mean error in our work are equal to those of Carney (1979), for [Fe/H] >= -1.75 dex where Carney&#39;s calibration is valid.