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 .