The $R$-Process Alliance: First Release from the Southern Search for
  $r$-Process-Enhanced Stars in the Galactic Halo
  The recent detection of a binary neutron star merger and the clear evidence
for the decay of radioactive material observed in this event have, after sixty
years of effort, provided an astrophysical site for the rapid neutron-capture
($r$-) process which is responsible for the production of the heaviest elements
in our Universe. However, observations of metal-poor stars with highly-enhanced
$r$-process elements have revealed abundance patterns suggesting that multiple
sites may be involved. To address this issue, and to advance our understanding
of the $r$-process, we have initiated an extensive search for bright ($V <
13.5$), very metal-poor ($\mathrm{[Fe/H]} < -2$) stars in the Milky Way halo
exhibiting strongly-enhanced $r$-process signatures. This paper presents the
first sample collected in the Southern Hemisphere, using the echelle
spectrograph on du Pont 2.5m telescope at Las Campanas Observatory. We have
observed and analyzed 107 stars with $-3.13 < \mathrm{[Fe/H]} < -0.79$. Of
those, 12 stars are strongly enhanced in heavy $r$-process elements ($r$-II),
42 stars show moderate enhancements of heavy $r$-process material ($r$-I), and
20 stars exhibit low abundances of the heavy $r$-process elements and higher
abundances of the light $r$-process elements relative to the heavy ones
(limited-$r$). This search is more successful at finding $r$-process-enhanced
stars compared to previous searches, primarily due to a refined target
selection procedure that focuses on red giants.
