Chemical abundances in a high velocity RR Lyrae star near the bulge
  Low-mass, variable, high-velocity stars are interesting study cases for many
aspects of Galactic structure and evolution. Until recently, the only known
high- or hyper-velocity stars were young stars thought to originate from the
Galactic centre. Wide-area surveys like APOGEE and BRAVA have found several
low-mass stars in the bulge with Galactic rest-frame velocities larger than 350
km/s. In this study we present the first abundance analysis of a low-mass, RR
Lyrae star, located close to the Galactic bulge, with a space motion of ~ -400
km/s. Using medium-resolution spectra, we derive abundances (including upper
limits) of 11 elements. These allow us to chemically tag the star and discuss
its origin, although our derived abundances and metallicity, at [Fe/H] =-0.9
dex, do not point toward one unambiguous answer. Based on the chemical tagging,
we cannot exclude that it originated in the bulge. However, combining its
retrograde orbit and the derived abundances suggests that the star was
accelerated from the outskirts of the inner (or even outer) halo during
many-body interactions. Other possible origins include the bulge itself, or the
star could be stripped from a star cluster or the Sagittarius dwarf galaxy when
it merged with the Milky Way.
