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Recent spectroscopic explorations of large Galactic stellar samples starshave revealed the existence of red giants with [$\alpha$/Fe] ratios that areanomalously high, given their relatively young ages. We revisit the GALAH DR3survey to look for both dwarfs and giants with extreme [$\alpha$/Fe] ratios,that is, the upper 1% in the [$\alpha$/Fe]-[Fe/H] plane over the range in[Fe/H] between -1.1 and +0.4 dex. We refer to these outliers as "ex$\alpha$fe"stars. We used the GALAH DR3 data and their value-added catalog to trace theproperties (abundances, masses, ages, and kinematics) of the ex$\alpha$festars. We investigated the effects of secular evolution and the magnitudelimitations of GALAH to understand the mass and metallicity distributions ofthe sample stars. We also discuss the corresponding biases in previous studiesof stars with high [$\alpha$/Fe] in other surveys. We find both dwarf and giantex$\alpha$fe stars younger than 3 Gyr, which we refer to as "y-ex$\alpha$fe"stars. Dwarf y-ex$\alpha$fe stars exhibit lithium abundances similar to thoseof young [$\alpha$/Fe]-normal dwarfs at the same age and [Fe/H]. In particular,the youngest and most massive stars of both populations exhibit the highest Liabundances, A(Li)~3.5 dex (i.e., a factor of 2 above the protosolar value),while cooler/older stars exhibit the same Li depletion patterns increasing withboth decreasing mass and increasing age. In addition, the [Fe/H] and massdistributions of both the dwarf and giant y-ex$\alpha$fe stars do not differfrom those of their [$\alpha$/Fe]-normal counterparts found in the thin diskand they share the same kinematic properties. We conclude that y-ex$\alpha$fedwarfs and giants are indeed young, their mass distribution shows nopeculiarity, and they differ from young [$\alpha$/Fe]-normal stars by theirextreme [$\alpha$/Fe] content only. However, their origin remains unclear.

Lithium, masses, and kinematics of young Galactic dwarf and giant stars with extreme [$\alpha$/Fe] ratios