New Metallicity Calibration Down to [Fe/H] = −2.75 dex

Abstract

Abstract:We have taken 88 dwarfs, covering the colour-index interval 0.37 ≤ (B−V) 0 ≤ 1.07 mag, with metallicities −2.70 ≤ [Fe/H] ≤+ 0.26 dex, from three different sources for new metallicity calibration. The catalogue of Cayrel de Strobel 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. In constructing the new calibration we have used as 'corner stones' 77 stars which supply at least one of the following conditions: (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 • ; (ii) the parallax is rather large, if the galactic latitude is absolutely low and vice versa. Contrary to previous investigations, a third-degree polynomial is fitted for the new calibration: [Fe/H] = 0.10 − 2.76δ − 24.04δ 2 + 30.00δ 3 . The coefficients were evaluated by the least-squares method, without regard to 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)

An Improved Metallicity Calibration with UBV Photometry

“…There is no overlap between stars in the two sets just mentioned and the sample stars. The results for the data of Karaali et al (2003) are given in Table 4. that there are statistical differences between the two calibrations.…”

“…We applied these calibrations to two sets of data with À1.76 # [Fe/H] # 0.4 dex taken from Karaali et al (2003) and Karatas -& Schuster (2006) and we compared the evaluated metallicities with the original ones for two calibrations. The metallicities of 75 stars in the first set were estimated spectroscopically, whereas those for 469 stars are based on photometry.…”

“…We derived metallicity calibrations for two sets of guillotine factors using the same procedure and applied them to two different sets of data. The data of the first set were taken from Karaali et al (2003), whereas those of the second set are from Karatas -& Schuster (2006). For the first set, the mean deviations of the residuals for two calibrations are different.…”

“…One can estimate guillotine factors for a larger set of B À V colours by applying an interpolation formula to the data in Table 1. This is the case in some of our works (Karaali et al 2003;Ak et al 2007aAk et al , 2007bYaz & Karaali 2010). Carney (1979) normalized the ultraviolet excesses of 101 dwarfs by using the procedure of Sandage (1969) and calibrated them to the metal abundance [Fe/H].…”

“…This calibration could be used to evaluate metal abundances in the U BV photometry. Karaali et al (2003) improved this calibration by using a different procedure and a different set of U BV data. Other works in different photometries followed the ones carried out in the U BV for metallicity estimation.…”