The R-Process Alliance: Discovery of a low-alpha, r-Process-Enhanced
  Metal-Poor Star in the Galactic Halo
  A new moderately r-process-enhanced metal-poor star, RAVE J093730.5-062655,
has been identified in the Milky Way halo as part of an ongoing survey by the
R-Process Alliance. The temperature and surface gravity indicate that
J0937-0626 is likely a horizontal branch star. At [Fe/H] = -1.86, J0937-0626 is
found to have subsolar [X/Fe] ratios for nearly every light, alpha, and Fe-peak
element. The low [alpha/Fe] ratios can be explained by an ~0.6 dex excess of
Fe; J0937-0626 is therefore similar to the subclass of "iron-enhanced"
metal-poor stars. A comparison with Milky Way field stars at [Fe/H] = -2.5
suggests that J0937-0626 was enriched in material from an event, possibly a
Type Ia supernova, that created a significant amount of Cr, Mn, Fe, and Ni and
smaller amounts of Ca, Sc, Ti, and Zn. The r-process enhancement of J0937-0626
is likely due to a separate event, which suggests that its birth environment
was highly enriched in r-process elements. The kinematics of J0937-0626, based
on Gaia DR2 data, indicate a retrograde orbit in the Milky Way halo; J0937-0626
was therefore likely accreted from a dwarf galaxy that had significant
r-process enrichment.
