Metallicity Gradient in the Disk of the Galaxy from $uvby$-$\beta$-Ca Photometry of F and G Supergiant Stars
Session 22 -- Galactic Structure; Galactic Center
Display presentation, Monday, 9, 1995, 9:20am - 6:30pm

## [22.01] Metallicity Gradient in the Disk of the Galaxy from $uvby$-$\beta$-Ca Photometry of F and G Supergiant Stars

John M. Powell (Brigham Young University)

New $uvby$--$\beta$--Ca photometry of F and G supergiant stars in Milky Way Galaxy clusters, associations, and binary systems and in the Magellanic Clouds are used to empirically derive intrinsic $b$--$y$ color for yellow supergiants. The reddening independent indices [$m_1$], [$c_1$], and [hk] are used to derive a surface gravity indicator $\delta$[$c_1$] and a metallicity indicator $\delta$[hk]. The metal abundance dependence of [$m_1$] is corrected for by using photometry of LMC and SMC supergiants. Semi-empirical calibrations of temperature, surface gravity, and metallicity are derived using extant spectroscopically-derived values. The results are compared with the newest (1994) Kurucz atmospheric models. A mass-dependent luminosity calibration is also derived. The calibrations are used to estimate the galactic radial position and metallicity of the supergiants in order to derive the metallicity gradient in the disk.