The [Fe/H] Dependence on the Ca<scp>ii</scp>-MVRelationship

We have examined the Wilson–Bappu effect, a relationship between the absolute magnitude of the star, MVMV, and the logarithm of the Ca ii emission width, W0W0, over the largest MVMV range to date, +13+13 to -5-5, covering MM-dwarfs to type Ia supergiants. We used an extensive literature, the latest Hipparcos reduction, data from two globular clusters, and new observations from Apache Point Observatory to compile a sample that allowed us to study the effect of [Fe/H] on the Wilson–Bappu relationship. Our results include reporting the deviations from linearity and demonstrating that the Wilson–Bappu relationship is insensitive to metallicity.