MASS-LOSS AND THE EVOLUTION OF PLANETARY-NEBULA NUCLEI

The paper discusses observational aspects of uncertainties in the evol ution of planetary nebula nuclei (PNNi) due to mass loss. Adopting dif ferent scenarios for the zero-age point and the post-AGB wind we inves tigate the positions of the theoretical tracks on diagrams for observa tional determinations of the PNN masses. We find that within a reasona ble range of the mass loss parameters the modifications of the PNN tra cks are rather modest. The resultant uncertainty in the observed PNN m ass is about or lower than 0.02 M..