New empirical metal abundance calibrations for Washington photometry of G and K giants

An analysis of Washington photometric data of red giants in general galactic globular clusters demonstrates that the Washington abundance calibrations are affected by systematic errors due to the decrease of abundance sensitivity of (C-M) with the temperature. In this work we investigate and revise the existing abundance calibrations. Using new CMT1T2 data of red giants in open clusters: (1) we redefine the fiducial lines for [M/H] = 0.0 in the colour-colour diagrams; (2) we demonstrate that the above mentioned effect depends on the metallicity, and (3) we obtain new empirical metal abundance calibrations. The individual CMT1T2 observations as well as the detailed results obtained in this study will be published elsewhere.Asociación Argentina de Astronomí