The GALAH Survey: Accreted stars also inhabit the Spite Plateau
We present lithium abundances for 105 dwarf stars in the halo of the Milky Way that were accreted as part of the Gaia-Enceladus-Sausage (GES). We use these stars to investigate the ``cosmological lithium problem'' --- the observed discrepancy between the amount of lithium in old, metal-poor dwarf stars in our Galaxy, and the amount of lithium predicted to have been produced during the Big Bang. In particular, we investigate whether the formation environment of stars plays a role in the lithium abundance and scatter of the Spite Plateau. These stars from GES present a unique opportunity to investigate the lithium abundance of a large population of extra-Galactic dwarf stars, and were observed and analyzed as part of the Third Data Release of the GALactic Archeology with HERMES (GALAH) survey. We use orbital actions to select samples of GES stars, halo stars, and disk stars, finding that the GES stars show the same lithium abundance as both other accreted stars, and \textit{in situ} Milky Way stars, confirming that that the “lithium problem” is not related to the formation environment.
