Evolution of the carbon and oxygen isotopes in the Galaxy

The evolution of the C and O isotopes in our Galaxy is studied, on the basis of recent results of stellar nucleosynthesis and recent models for the chemical evolution of the galactic disk. It is found that has a mixed primary and secondary origin, the former presumably from hot-bottom burning or from some other mechanism mixing protons with ^12^C synthesized in the star itself; both mechanisms may take place in intermediate mass stars. is of purely secondary origin and is produced in stars of all masses; its yields given by various authors are overestimated, probably because of the use of low (p,α) and (p,γ) rates. The ^18^O "puzzle" is quantitatively investigated and several solutions are considered, like the possibility of the solar system to have been formed in an OB association. The possibility of an error in the measured ^18^O abundance alone, either in the interstellar medium or in the solar system, is also considered and shown to offer a simple solution to that puzzle.