Calculation of [α/Fe] from stellar evolution models with individually altered abundances of O, Ne, Mg, Si, S, Ca and Ti

In this work, we analyze how variations in the abundances of α elements affect the physical properties of stars and provide a method to calculate [α/Fe] from stellar models with individually altered abundances. We compute a grid of stellar evolution models using GARSTEC, covering masses from 0.6 to 2.0 M⊙ and [Fe/H] from -2.6 to +0.6 dex, with variations of ±0.2, ±0.4, and ±0.6 dex in O, Ne, Mg, Si, S, Ca, and Ti abundances. This grid allows us to reproduce stellar tracks with arbitrary abundance patterns of α elements through linear addition. To mimic traditional α-enhancement, where all elemental abundances increase equally, we estimate [α/Fe] by minimizing log L/L⊙ and log T from stellar models and the target star’s chemical composition. We validate our method with chemical data from several target stars in the APOGEE experiment and analyze the sensitivity of [α/Fe] on the stellar mass and [Fe/H]. Finally, we apply this method to the entire APOGEE.