New models for the evolution of Post-Asymptotic Giant Branch stars and Central Stars of Planetary Nebulae
The Post Asymptotic Giant Branch (AGB) phase is arguably one of the least understood phases of the evolution of low- and intermediate- mass stars. The two grids of models presently available are based on outdated micro- and macro-physics and do not agree with each other. We study the timescales of post-AGB and CSPNe in the context of our present understanding of the micro- and macro-physics of stars. We want to assess whether new post-AGB models, based on the latter improvements in TP-AGB modeling, can help to understand the discrepancies between observation and theory and within theory itself. We compute a grid of post-AGB full evolutionary sequences that include all previous evolutionary stages from the Zero Age Main Sequence to the White Dwarf phase. Models are computed for initial masses between 0.8 and 4 $M_\odot$ and for a wide range of initial metallicities ($Z_0=$0.02, 0.01, 0.001, 0.0001), this allow us to provide post-AGB timescales and properties for H-burning post-AGB objects with masses in the relevant range for the formation of planetary nebulae ($\sim$ 0.5 - 0.8, $M_\odot$). We find post-AGB timescales that are at least $\sim 3$ to $\sim 10$ times shorter than those of old post-AGB stellar evolution models. This is true for the whole mass and metallicity range. The new models are also $\sim$ 0.1 - 0.3 dex brighter than the previous models with similar remnant masses. Post-AGB timescales show only a mild dependence on metallicity. The shorter post-AGB timescales derived in the present work are in agreement with recent semiempirical determinations of the post-AGB timescales from the CSPNe in the Galactic Bulge. Due to the very different post-AGB crossing times, initial-final mass relation and luminosities of the present models, they will have a significant impact in the predictions for the formation of planetary nebulae and the planetary nebulae luminosity function.