New asymptotic giant branch models for a range of metallicities

摘要

We present a new grid of stellar model calculations for stars on the Asymptotic Giant Branch between 1.0 and 6.0 Mo. Our gridconsists of 10 chemical mixtures with 5 metallicities between Z = 0.0005 and Z = 0.04, and with both solar-like and a-elementenhanced metal ratios for each metallicity. We treat consistently the carbon-enhancement of the stellar envelopes by using opacitytables with varying C/O-ratio and by employing theoretical mass loss rates for carbon stars. The low temperature opacities have beencalculated specifically for this project. For oxygen stars we use an empirical mass loss formalism. The third dredge-up is naturallyobtained by including convective overshooting. Our models reach effective temperatures in agreement with earlier synthetic models,which included approximative carbon-enriched molecular opacities and show good agreement with empirically determined carbon-star lifetimes. A fraction of the models could be followed into the post-AGB phase, for which we provide models in a mass rangesupplementing previous post-AGB calculations. Our grid constitutes the most extensive set of AGB-models, calculated with the latestphysical input data and treating carbon-enhancement due to the third dredge-up most consistently.