The Variable Stars and Blue Horizontal Branch of the Metal-rich Globular Cluster NGC 6441

We present time-series VI photometry of the metal-rich ([Fe/H] = -0.53) globular cluster NGC 6441. Our color-magnitude diagram shows that the extended blue horizontal branch seen in Hubble Space Telescope data exists in the outermost reaches of the cluster. About 17% of the horizontal-branch stars lie blueward and brightward of the red clump. The red clump itself slopes nearly parallel to the reddening vector. A component of this slope is due …