Oxygen Isotopes from Massive Stars

We investigate the yields of the three stable oxygen isotopes 16;17;18 O and their dependence on weakly constrained physical ingredients in pre-supernova models. We show that the 16 O yield is sensitive to assumptions on convection used in evolutionary models for massive stars. In addition to that, stellar wind mass loss aaects the 16 O yield of Galactic stars initially more massive than 30 M. We show that the production factor of 17 O in massive stars is strongly increasing with metallicity, contrary to the expectation of a constant production factor for secondary isotopes. The 18 O yield is extremely sensitive to the treatment of convection in regions of varying mean molecular weight in the stellar interior. The Galactic distribution of all three oxygen isotopes has a large diagnostic potential for chemical evolution models, but also for uncertain stellar physics as mass loss and convection.