The s-process in stellar population synthesis: a new approach to understanding AGB stars

We find that galactic disk objects are reproduced by a spread of a factor of two in the effectiveness of the 13C neutron source. Lower metallicity objects can be reproduced only by lowering the average value of the effectiveness of the 13C neutron source needed for the galactic disk objects by at least a factor of 3. Using observations of s-process elements in post-AGB stars as constraints we find that dredge-up has to start at a lower core mass than predicted by current theoretical models, that it has to be substantial (λ >∼ 0.2) in stars with mass M