Nine New Metal-Poor Stars on the Subgiant and Red Horizontal Branches
  with High Levels of r-process Enhancement
  We report the discovery of nine metal-poor stars with high levels of
r-process enhancement (+0.81<[Eu/Fe]<+1.13), including six subgiants and three
stars on the red horizontal branch. We also analyze four previously-known
r-process-enhanced metal-poor red giants. From this sample of 13 stars, we draw
the following conclusions. (1) High levels of r-process enhancement are found
in a broad range of stellar evolutionary states, reaffirming that this
phenomenon is not associated with a chemical peculiarity of red giant
atmospheres. (2) Only 1 of 10 stars observed at multiple epochs shows radial
velocity variations, reaffirming that stars with high levels of r-process
enhancement are not preferentially found among binaries. (3) Only 2 of the 13
stars are highly-enhanced in C and N, indicating that there is no connection
between high levels of r-process enhancement and high levels of C and N. (4)
The dispersions in [Sr/Ba] and [Sr/Eu] are larger than the dispersions in
[Ba/Eu] and [Yb/Eu], suggesting that the elements below the second r-process
peak do not always scale with those in the rare earth domain, even within the
class of highly-r-process-enhanced stars. (5) The light-element (12<Z<30)
abundances of highly-r-process-enhanced stars are indistinguishable from those
with normal levels of r-process material at the limit of our data, 3.5 per cent
(0.015 dex) on average. The nucleosynthetic sites responsible for the large
r-process enhancements did not produce any detectable light-element abundance
signatures distinct from normal core-collapse supernovae.
