Lithium and Beryllium in NGC 752 -- An Open Cluster Twice the Age of the
  Hyades
  The surface abundances of the light elements lithium (Li) and beryllium (Be)
reveal information about the physical processes taking place in stellar
interiors. The investigation of the amount of these two elements in stars in
open clusters shows the effect of age on those mechanisms. We have obtained
spectra of both Li and Be in main-sequence stars in NGC 752 at high spectral
resolution and high signal-to-noise ratios with HIRES on the Keck I telescope.
In order to make meaningful comparisons with other clusters, we have determined
the stellar parameters on a common scale. We have found abundances of Li and Be
by spectral synthesis techniques. NGC 752 is twice the age of the well-studied
Hyades cluster. We find that 1) The Li dip centered near 6500 K is wider in NGC
752, having expanded toward cooler temperatures; 2) The Be dip is deeper in the
older NGC 752; 3) The Li "peak" near 6200 K is lower by about 0.3 dex; 4)
Although there is little Be depletion in the cooler stars, it is possible that
Be may be lower in NGC 752 than in the Hyades; 5) The Li content in both
clusters declines with decreasing temperature, but there is less Li in NGC 752
at a given temperature by $\sim$0.4 dex. These differences are consistent with
the transport of the light-element nuclei below the surface convection zone as
predicted by theory. That connection to rotational spin-down is indicated by
the pattern of rotation with temperature in the two clusters.
