C and N abund. and isochrone fitting in 47 Tuc

While UV photometry and light-element abundances (e.g., Na and O) are commonly used, the optical V vs. (V-I) color-magnitude diagram (CMD) is often assumed to be relatively unaffected by such inhomogeneities and is typically used to derive basic cluster parameters. On the other hand, C and N would be the best chemical tracers of these variations but are challenging to measure due to their spectral features lying in the blue/UV or IR regions.

In this study, we investigate chemical variations in the globular cluster NGC104 (47Tucanae), aiming to trace multiple stellar populations across evolutionary phases and examine how the C/N anti-correlation evolves from the main sequence (MS) to the asymptotic giant branch (AGB). We also assess the impact of these populations on the interpretation of the V vs. V-I diagram. Using spectra spanning all evolutionary stages, we derive [C/Fe] and [N/Fe] abundances for a large stellar sample.