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The Abundance of Oxygen in M92 Giants

Published online by Cambridge University Press:  12 April 2016

Catherine A. Pilachowski
Catherine A. Pilachowski*
Affiliation:
National Optical Astronomy Observatories Kitt Peak National Observatory, *PO Box 26732, Tuscon, AZ 85726-6732, USA

Extract

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Studies of the carbon and nitrogen abundances in metal poor giants have generally supported the models of Sweigart and Mengel (1979) which indicate the action of meridional circulation in CN-processing metal poor red giant envelopes. Carbon et al. (1982) find the trends in the carbon and nitrogen abundances in M 92 stars to be at least qualitatively consistent with CN-cycle processing of the envelope, but stars at all phases of giant branch evolution have unusual, and unexplained, carbon and nitrogen abundances. The oxygen abundance is the missing piece of information which may explain what’s going on. Sweigart and Mengel’s models suggest that ON-processing might also occur in the most metal poor giants. The sample of giants in M 92 for which Carbon et al. have provided carbon and nitrogen abundances is ideal for the determination of oxygen abundances to look for the effects of ON-processing. Once the oxygen abundances are known, the sum C+N+0 can be computed to see if it is constant along the giant branch or varies from star to star.

Type
Part I. Chemical Peculiarities as Probe of Stellar Evolution
Information
International Astronomical Union Colloquium , Volume 108: Atmospherics Diagnostics of Stellar Evolution: Chemical Peculiarity, Mass Loss, and Explosion , 1988 , pp. 46 - 47
Copyright
Copyright © Springer-Verlag 1988

References

Carbon, D.F., Langer, G.E., Butler, D., Draft, R.P., Suntzeff, N. B., Kemper, E., Trefzger, C.F., and Romanishin, W. 1982, Ap. J. Suppl., 49, 207 Google Scholar
Sweigart, A. and Mengel, J. 1979, Ap. J. 229, 642.Google Scholar