New data on young and old black holes and other unexpected creatures

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

Recent observations have revealed a population of $α$-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 ($τ<6$Gyr) incompatible with the canonical Galactic chemical evolution scenario. Here we study the chemistry and kinematics of a large sample of such $α$-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-$α$ old ste…