Mixing and the strong-cyanogen phenomenon

Journal Article · Mon May 15 04:00:00 EDT 1978 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/156140· OSTI ID:7054773

Deming, D

A model atmosphere and spectrum synthesis calibration has been obtained for the cyanogen band strength index of DDO photometry. Synthetic 41-42 indices have been computed in the DDO system for a variety of CNO compositions chosen to schematically represent varying degrees of mixing from a hydrogen-burning shell. Only a slight strengthening of the CN index, deltaCN, is found for the degree of mixing from a hydrogen-burning shell which is predicted by standard stellar evolution calculations before and during core helium burning of 1-3 M/sub sun/ stars. Greater amounts of mixing, such as would be produced by extensive meridional mixing on the main sequence, result in a greater weakening of the CN band strength than is observed. Modest amounts of mass loss, followed by deep mixing, cannot be ruled out on the basis of CN strengths for stars on the first ascent of the giant branch. Existing stellar evolution calculations for the first ascent of the giant branch are consistent with the CN band strengths of metal-rich stars. A theoretical calibration of deltaCN in terms of (metals/H) has been obtained and is in reasonable agreement with the existing empirical calibration. It is concluded that the majority of strong-CN Population I stars are more likely to be super-metal-rich than nitrogen-rich. High-dispersion studies of such stars are not in disagreement with this conclusion when the high-dispersion abundances are corrected to a conventional value of the Hyades abundance and when reasonably large (N > or approx. =10) samples of stars are studied. Large samples of stars show that a definite mean relation exists between CN strength and metal abundance, although individual stars may deviate from the mean relation. The large enhancements of the CN bands which have been observed in globular clusters imply much larger enhancements of nitrogen abundance than are observed for Population I stars.

• Research Organization: Astronomy Program, University of Maryland at College Park
• OSTI ID: 7054773
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 222:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
CARBON
CHEMICAL COMPOSITION
CHEMISTRY
COSMOCHEMISTRY
CRYOGENIC FLUIDS
CYANOGEN
ELEMENTS
ENERGY SPECTRA
FLUIDS
MATHEMATICAL MODELS
NITROGEN
NONMETALS
NUCLEOSYNTHESIS
PHOTOMETRY
SPECTRA
STAR MODELS
STARS
STELLAR ATMOSPHERES