thesis - IRS, The Infrared Spectrograph

84 CHAPTER 5: Probing AGB nucleosynthesis via accurate Planetary Nebula abundancesFigure 5.3–. Comparison between measured PN abundances (squares with errors bars) and modelpredictions (diamonds). Two estimates for the oxygen abundance for the Sun are also indicated, O ⊙High and O ⊙ Low (see Table 5.4 and text). In each panel the sequence of diamonds denotes the expectedPN abundance as a function of the stellar progenitor’s mass, increasing from 0.9 to 5.0 M ⊙ (a few valuesare labeled along C/H curve), and for initial solar metallicity Z = 0.019. The initial O abundance wasset equal to O ⊙ High. The model assumptions adopted for the TP-AGB evolution, corresponding tocase A) of Table 5.4, include solar-scaled molecular opacities (κ fix ), and third dredge-up efficiencyλ = 0.5.