Lithium abundance in a turnoff halo star on an extreme orbit
  The lithium abundance in turnoff stars of the old population of our Galaxy is
remarkably constant in the metallicity interval -2.8\textless{}[Fe/H]
\textless{}-2.0, defining a plateau. The Li abundance of these turnoff stars is
clearly lower than the abundance predicted by the primordial nucleosynthesis in
the frame of the standard Big Bang nucleosynthesis. Different scenarios have
been proposed for explaining this discrepancy, along with the very low scatter
of the lithium abundance around the plateau. The recently identified very high
velocity star, WISE J072543.88-235119.7 appears to belong to the old Galactic
population, and appears to be an extreme halo star on a bound, retrograde
Galactic orbit. In this paper, we study the abundance ratios and, in particular
the lithium abundance, in this star. The available spectra (ESO-Very Large
Telescope) are analyzed and the abundances of Li, C, Na, Mg, Al, Si, Ca, Sc,
Ti, Cr, Mn, Fe, Co, Ni, Sr and Ba are determined.The abundance ratios in WISE
J072543.88-235119.7 are those typical of old turnoff stars. The lithium
abundance in this star ~is in close agreement with the lithium abundance found
in the metal-poor turnoff stars located at moderate distance from the Sun. This
high velocity star confirms, in an extreme case, that the very small scatter of
the lithium plateau persists independent of the dynamic and kinematic
properties of the stars.
