The carbon monoxide band strength and 12C/13C ratio in K giants.

The first overtone vibration-rotation bands of CO have been studied in the spectra of 15 giants, G8-K5. CN-strong stars are found to be characterized by CO band-strength excess, and it is argued that a true abundance difference must be responsible. Spectral synthesis is employed to deduce a 12C/13C ratio of about 10 for four normal K giants and a Boo. The normal giants appear to have a carbon abundance near the solar value. The CN-strong, super-metal-rich a Ser is distinguished by a relative 13C deficiency. Subject headings: abundances, stellar - late-type-stars - molecules