A UVBY-BETA PHOTOMETRIC CALIBRATION OF IRON ABUNDANCES IN SUPERGIANT STARS

A photometric reddening-free calibration for [Fe/H] valid far giant an d supergiant stars of intermediate temperature, has been obtained usin g the Stromgren uvby beta system. Galactic supergiants, supergiants in the Magellanic Clouds and Galactic metal deficient red giants with sp ectroscopic determinations of [Fe/H] were used as calibrators. The cal ibration can be used to predict [Fe/H] with an accuracy of 0.33 dex, v alid for stars with 0.14 < [m(1)] < 0.70 in the iron abundance range - 2.5 < [Fe/H] < +0.3. This shows the potential of supergiant stars as t racers of iron abundances in other galaxies. Evidence that Galactic lu minous F-G stars are intrinsically bluer than their counterparts in th e Magellanic Clouds is offered.