Late stages of stellar evolution. II - Mass loss and the transition of asymptotic giant branch stars into hot remnants

Computations have been made of the transition of asymptotic branch giants of 0.8 and 1.0 solar mass into remnants of 0.565, 0.553, and 0.546 solar mass by means of mass loss which removed the stellar envelopes in about 1000 yr. The remnants were then evolved across the H-R diagram to the white dwarf configuration and their relevance for central stars of planetary nebulae studied. From the temporal evolution of these models, lower limits have been determined for mass and luminosity of central stars of about 0.55 and 2500 solar masses. These computations also made it possible to study the importance of final thermal pulses on the evolution of central stars. It is very likely that these instabilities are responsible for the rapid evolution of FG Sge. They may also be responsible for some peculiar planetaries which show helium-enriched matter near their nuclei.