By using updated stellar low mass stars models , we can systematically investigate the nucleosynthesis processes occurring in AGB stars , when these objects experience recurrent thermal pulses and third dredge-up episodes .
In this paper we present the database dedicated to the nucleosynthesis of AGB stars : the FRUITY ( FRANEC Repository of Updated Isotopic Tables & Yields ) database .
An interactive web-based interface allows users to freely download the full ( from H to Bi ) isotopic composition , as it changes after each third dredge-up episode and the stellar yields the models produce .
A first set of AGB models , having masses in the range 1.5 \leq M / M _ { \odot } \leq 3.0 and metallicities 1 \times 10 ^ { -3 } \leq Z \leq 2 \times 10 ^ { -2 } , is discussed here .
For each model , a detailed description of the physical and the chemical evolution is provided .
In particular , we illustrate the details of the s -process and we evaluate the theoretical uncertainties due to the parametrization adopted to model convection and mass loss .
The resulting nucleosynthesis scenario is checked by comparing the theoretical [ hs/ls ] and [ Pb/hs ] ratios to those obtained from the available abundance analysis of s -enhanced stars .
On the average , the variation with the metallicity of these spectroscopic indexes is well reproduced by theoretical models , although the predicted spread at a given metallicity is substantially smaller than the observed one .
Possible explanations for such a difference are briefly discussed .
An independent check of the third dredge-up efficiency is provided by the C-stars luminosity function .
Consequently , theoretical C-stars luminosity functions for the Galactic disk and the Magellanic Clouds have been derived .
We generally find a good agreement with observations .