SIMBAD references

A new calibration of the Stroemgren (b-y), m₁ diagram in terms of iron abundance of red giants is presented. This calibration is based on a homogeneous sample of giants in the globular clusters ω Centauri, M 22, and M 55 as well as field giants from the list of Anthony-Twarog & Twarog (1998AJ....116.1922A). Towards high metallicities, the new calibration is connected to a previous calibration by Grebel & Richtler (1992A&A...253..359G), which was unsatisfactory for iron abudances lower than -1.0dex. The revised calibration is valid for CN-weak/normal red giants in the abundance range of -2.0<[Fe/H]<0.0dex, and a color range of 0.5<(b-y)<1.1mag. As shown for red giants in ω Centauri, CN-weak stars with Stroemgren metallicities higher than -1.0dex cannot be distinguished in the (b-y), m₁ diagram from stars with lower iron abundances but higher CN band strengths.