Speaker
Description
Carbon-rich AGB stars are the primary source of carbon in the universe. Oxygen-rich AGB stars are generally characterized by the presence of TiO in their visible spectra whereas carbon-rich AGB stars present mainly C2 and CN in visible spectra. We present MESA models combined with output from GRYE of advanced AGB stars focusing on the third dredge-up and the enhancement of the C/O ratio. Opacity tables supplied by Ferguson et al. (2005) are based on oxygen-rich abundances and may not be appropriate for carbon-rich environments. As the C/O ratio increases, the amount of H2O decreases in favor of carbon species such as CN, HCN, and CO. This affects the low-temperature opacities in a significant way and impacts other aspects of MESA models. Using GYRE, we compute pulsation periods for different low-temperature opacity calculations to evaluate how parameters such as the stellar age of onset AGB phase and maximum pulsation period changes. Our analysis reveals that systematically varying the initial stellar mass and metallicity induces non-linear trends in period difference and age shift that arise due to changing opacities.