Speaker
Description
Evidence of the CNO cycle can be observed in the atmospheres of K and M giant stars through their surface carbon isotope ratios. For the isotopes standard stellar evolution models predict a decrease in the C12/ C13 ratio to drop from values of about 70 to roughly 20 after first dredge-up. However, observations reveal ratios as low as 5, close to the CNO-cycle equilibrium value, providing strong evidence for non-canonical mixing processes in red giants. In addition, the carbon isotopic ratio is a powerful diagnostic of the evolutionary stage of cool giant stars.
In this work, we analyze high-resolution near-infrared spectra obtained with IGRINS for a sample of field red giants in the solar neighborhood. We determine the ratio using well-defined CO molecular features and perform the spectral analysis with pySME. Our sample spans a range in effective temperature and metallicity, allowing us to investigate potential correlations between the carbon isotopic ratio and other stellar parameters. Ultimately, we aim to combine our isotopic ratio measurements with asteroseismic constraints from Kepler for a subset of the sample, in order to better link surface mixing signatures with precise evolutionary states.