Limitations of CN and CH Molecular Band Strengths at High Metallicities: A Case Study in NGC 6791

We present an analysis of the CN and CH molecular band strengths in NGC 6791 from low-resolution Sloan Extension for Galactic Understanding and Exploration spectra as a means to detect chemical variations in the cluster. NGC 6791 is a heavily studied open cluster (OC) due to its unique combination of old age, high mass, and high metallicity. These characteristics place NGC 6791 between the physical properties of most globular and OCs. Recent photometric and spectroscopic studies yield contradicting results, with some claiming to detect signs of multiple populations, as in globular clusters, while others do not. We do not find large spreads in the CN and CH band strength distributions that would suggest multiple populations. By pairing spectral synthesis with the measured CN values, we conclude that the maximum [N/Fe] variation in the cluster is 0.2 dex. Additionally, we find that the saturation of the CH band at high metallicities limits its usefulness in detecting multiple populations and determining C abundances.