OGLE-III Detection of the Anomalous Galactic Bulge Red Giant Branch
  Bump: Evidence of Enhanced Helium Enrichment
  We measure the red giant branch bump (RGBB) of the Galactic bulge, the most
metal-rich RGBB ever detected. The RGBB luminosity functions peaks at the
expected brightness, but its number density is very low relative to Galactic
globular cluster calibrations, implying the Galactic bulge has a higher helium
enrichment parameter {\Delta}Y/{\Delta}Z $\ge$ 4.0 for Y~0.35 rather than the
standard 2.0 with Y=0.27. The RGBB is (0.71 +/- 0.02) mag fainter than the red
clump (RC) in I toward the densest stellar regions imaged by the OGLE-III
Galactic bulge photometric survey, (|l| $\le$ 4, 2 <~ |b| $\le$ 4). The number
density of RGBB stars is (12.7 +/- 2.0)% that of RC stars. The brightness
dispersion of the RGBB is significantly lower than that of the RC, a result
that is difficult to explain as the luminosity of the RGBB is known to
significantly vary with metallicity. Sightlines toward the Galactic bulge that
have two RCs have two RGBBs with similar properties to one another, an expected
outcome if the Milky Way's bulge is X-shaped. We also find preliminary evidence
of the Galactic bulge asymptotic giant branch bump, at a brightness of ~1.1 mag
brighter than the RC in I and with a number density ~1.5% that of the RC.
Accounting for the RGBB has a small effect on the best-fit parameters of the
RC, shifting its best-fit peak brightness and reducing its brightness
dispersion by ~0.015 mag each.
