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Carbon and nitrogen abundances in red giant stars in the globular cluster 47 Tucanae

Journal Article · · Astrophys. J.; (United States)
DOI:https://doi.org/10.1086/157303· OSTI ID:5911043
; ;
The effects of changes in temperature, gravity, overall metal abundance, and carbon and nitrogen abundances have been investigated for model stellar spectra and colors representing globular cluster giants of moderate metal deficiency. The results are presented in the form of spectral atlases and theoretical color-color diagrams. Using these results, approximate abundances of carbon and nitrogen have been derived for some red giant stars in 47 Tuc, from intermediate- and low-dispersion spectra and from intermediate- and narrow-band photometry. In all the normal giants studied, nitrogen is overabundant by up to about a factor of 5 ( the precise value depends on the adopted carbon abundance), with different enhancements for different giants. Our observational material is not sufficient to distinguish between a normal carbon abundance and a slight carbon depletion for the giant-branch stars, but carbon appears to be somewhat depleted in stars on the asymptotic giant branch. A most probable value of (M/H)=-0.8 for the overall cluster metal abundance is suggested from analysis of Stroemgren photometry of red horizontal-branch stars.Some general comments are made about the power and limitations of analyses based on low-resolution synthetic spectra and/or synthetic colors.
Research Organization:
Royal Greenwich Observatory
OSTI ID:
5911043
Journal Information:
Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 232:2; ISSN ASJOA
Country of Publication:
United States
Language:
English

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Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
CARBON
CHEMICAL COMPOSITION
CHEMISTRY
COSMOCHEMISTRY
CRYOGENIC FLUIDS
ELEMENTS
ENERGY SPECTRA
FLUIDS
GIANT STARS
NITROGEN
NONMETALS
PHOTOMETRY
RED GIANT STARS
SPECTRA
STAR CLUSTERS
STARS