We present further analysis of the CN and CH molecular band strengths in NGC 6791 from low resolution SEGUE spectra as a means to detect chemical variations in the cluster. We attempt to measure the C and N abundances for the stars in our sample based on index measurements analyzed with the help of synthetic spectra produced by the Synthetic Spectrum Generator (SSG), which makes use of MARCS model atmospheres. These measurements combined with analysis of the CH and CN band strengths of globular and open clusters of varying metallicity taken from the SEGUE database suggest a saturation of the CH band occurring at metallicities above [Fe/H] ~ -0.7 that is not predicted by the models. This saturation effect limits the usefulness of the CH and CN bands in determining the C and N abundances in open clusters. However, the models continue to accurately predict the CN band strengths at high metallicities and are used to statistically determine the likelihood of two populations existing in NGC 6791. The statistical analysis confirms NGC 6791 is most likely to have only one CN population.
American Astronomical Society Meeting Abstracts #227
- Pub Date:
- January 2016