Peculiar Stars

CH star show strong bands of CH, CN. and C2

Ba stars are similar to CH stars, but are metal rich with no carbon enhancement. They are s-process element enriched (Ba and Sr). The Ba line at 4554. The Ch and Ba stars are often binary systems with white dwarf companions, the chemical enrichment may be due to mass transfer from the comapanion.

CNO stars are those that are either show some enrichment of C, N, or O, or some depletion of these elements. Typically late-O or early-B type.