Chemical Evolution of Mg Isotopes versus the Time Variation of the Fine Structure Constant

The low-z subset of the many-multiplet data from quasar absorption systems was explained using the isotopic ratios produced by the synthesis of ^25,26Mg at the base of the convective envelope in low-metallicity asymptotic giant branch stars. A model based on plausible expectations of stellar and galactic evolution was presented. Huge amounts of neutron-rich Mg isotopes were observed in metal-poor globular-cluster stars. The results show that the quasar absorption spectra may be the source of information on the nucleosynthetic history of such systems.