5 octobre 2017
Single stellar populations, being born from the same molecular cloud at virtually the same time, are often assumed to share the same chemical composition. While this assumption is quite accurate for the initial chemical composition of the stars, once stellar evolution sets in it does not hold any longer. Processes such as atomic diffusion, the first dredge-up and extra-mixing result in variations in the stellar surface chemical composition depending on their evolutionary stage. This has broad implications: e.g., atomic diffusion effects put a constraint to the precision achievable by chemical tagging methods, while the post-dredge-up [C/N] ratio can be used for the age-dating of field stars. Open clusters are ideal examples of single stellar populations and are therefore extremely useful for the study of stellar evolution. I will present an investigation of stellar evolutionary effects in the well-known old open cluster M67 based on high-resolution spectra from APOGEE and the Gaia-ESO Survey, including a comparison with the predictions of stellar evolutionary models.