Calibrating [C/N] Abundance Ratios Using Star Clusters To Determine Stellar Ages

Abstract

Through the use of large-scale surveys, astronomers are able to investigate Galactic evolution, both kinematically and chemically, however determining reliable stellar ages has been elusive. Surveys that provide high resolution spectroscopy can offer various elemental abundances in stellar populations of clusters and can be further used to constrain stellar ages. Using data from the Open Cluster Abundances and Mapping (OCCAM) survey, based on the SDSS/APOGEE-2 survey, we created a empirical relationship between open cluster stellar ages and the carbon-to-nitrogen ([C/N]) ratio abundances for evolved stars, primarily red giant branch stars. We explore how mixing effects in different stellar phases, like the red clump, affect the derived calibration. The [C/N]-age calibration cluster sample covers a wider range of ages and metallicities than previous calibrations and updates the calibration for the improved APOGEE DR17 abundance calibration. We verify that this [C/N]-age calibration is also consistent with astroseismic ages derived from Kepler photometry.