An R-process enhanced star in the dwarf galaxy Tucana III
  Chemically peculiar stars in dwarf galaxies provide a window for exploring
the birth environment of stars with varying chemical enrichment. We present a
chemical abundance analysis of the brightest star in the newly discovered
ultra-faint dwarf galaxy candidate Tucana III. Because it is particularly
bright for a star in an ultra-faint Milky Way satellite, we are able to measure
the abundance of 28 elements, including 13 neutron-capture species. This star,
DES J235532.66$-$593114.9 (DES J235532), shows a mild enhancement in
neutron-capture elements associated with the $r$-process and can be classified
as an $r$-I star. DES J235532 is the first $r$-I star to be discovered in an
ultra-faint satellite, and Tuc III is the second extremely low-luminosity
system found to contain $r$-process enriched material, after Reticulum II.
Comparison of the abundance pattern of DES J235532 with $r$-I and $r$-II stars
found in other dwarf galaxies and in the Milky Way halo suggests a common
astrophysical origin for the neutron-capture elements seen in all $r$-process
enhanced stars. We explore both internal and external scenarios for the
$r$-process enrichment of Tuc III and show that with abundance patterns for
additional stars it should be possible to distinguish between them.
