A number of G and K-type giants show either strong or weak molecular bands involving carbon. We illustrate two such stars here. HR 6791 is a G8 III (compare with the G8 III standard, Gem) with a weak CN 4216 band, and a very weak G-band (CH). Otherwise, the spectrum is fairly normal. HD 112127, a K2.5 III (compare with Leo, K2 III), on the other hand has an exceptionally strong CN 4216 band, seen here as a pronounced depression in the continuum shortwards of 4216 Å. In addition, it shows the 4737 Å C2 Swan band, and a clear depression of the continuum in the vicinity of 5200 , most probably due to the 5165 Å C2 Swan band. The strength of these molecular bands points to an abnormally high abundance of carbon in the atmosphere of this star.
This figure uses 3.6 Å resolution flux spectra.