Abundance anomalies in red giants with possible extragalactic origins
  unveiled by APOGEE-2
  By performing an orbital analysis within a Galactic model including a bar, we
found that it is plausible that the newly discovered stars that show enhanced
Al and N accompanied by Mg underabundances may have formed in the outer halo,
or were brought in by satellites field possibly accreted a long time ago.
However, another subsample of three N- and Al-rich stars with Mg-deficiency are
kinematically consistent with the inner stellar halo. A speculative scenario to
explain the origin of the atypical chemical composition of these stars in the
inner halo is that they migrated to the inner stellar halo as unbound stars due
to the mechanism of bar-induced resonant trapping.
