Metallicity of Red Clump Giants in Baade's Window

Abstract

The red clump giants are potentially very useful as standard candles. There is some controversy about the stability of their I-band absolute magnitude, but it does not seem to be serious. No controversy was anticipated about their colors, with metal rich giants expected to be redder and cooler than the metal poor giants. The purpose of this paper is to point out that no such correlation is apparent between [Fe/H] and effective temperature as determined with Washington CCD photometry for the giants in Baade's Window. No explanation is offered for this surprising result. It is also unknown why the galactic bulge red clump giants are redder than the clump giants near the Sun by 0.2 mag in the (V-I) color.