Most "young" $\alpha$-rich stars have high masses but are actually old

Understand

Recent observations have revealed a population of $\alpha$-element abundances enhanced giant stars with unexpected high masses ($\gtrsim$1 $M_\odot$) from asteroseismic analysis and spectroscopy.

• Assuming single-star evolution, their masses imply young ages ($\tau<6$Gyr) incompatible with the canonical Galactic chemical evolution scenario.
• Here we study the chemistry and kinematics of a large sample of such $\alpha$-rich, high-mass red giant branch (RGB) stars drawn from the LAMOST spectroscopic surveys.
• Using LAMOST and Gaia, we found these stars share the same kinematics as the canonical high-$\alpha$ old stellar population in the Galactic thick disk.