Elemental abundances in evolved supergiants. II. The young clusters h and chi Persei

摘要

We report on the results of our analyses of high-quality spectra of M supergiants in the h and chi Persei double cluster. Our temperature estimates range from 3500 to 4000 K for a sample of 14 stars. There is a wide range in the lithium abundances, from Li/Fe = -1.7 to Li/Fe = -0.10. The C-12/C-13 ratio ranges from 10 to 16 and displays a weak trend with luminosity, such that the more luminous stars have a slightly smaller ratio. We find a significant excess of Na, which may be due to its production by proton capture by Ne-22. However, there is no evidence for the O deficiency that usually accompanies a Na excess in globular cluster stars. References: 50