The Curious Radial Distributions of Horizontal Branch Stars in NGC 6441
  NGC 6441 is one of the most massive and most metal-rich globular clusters in
the galaxy, and is noted for an unusual extended horizontal branch which
reaches past the instability strip. We find evidence that there are two
different populations of stars within the heavily-populated red clump. Once a
differential reddening correction is applied, a large but compact group of
stars is found at the faint red end of the clump in the color magnitude
diagram. Brighter, bluer stars in the clump are found to be more centrally
concentrated within the cluster at very high level of significance. Curiously,
the blue horizontal branch stars show a more complex distribution, and are not
more centrally concentrated than the brighter red clump stars. The spatial
distributions of clump stars is in agreement with the idea that the the
brighter bluer part of the clump is a helium-enriched second generation. The
blue horizontal branch stars may be showing evidence that they are being
dynamically evaporated.
