Discontinuity in cyanogen strengths between giant stars of the disk and the halo

Journal Article · Tue Jan 15 04:00:00 EST 1980 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/157649· OSTI ID:5536155

Hartwick, F D.A.; McClure, R D

We compare the DDO CN index in different populations of giant stars and find that 1. Giant stars in 47 Tuc exhibiting the weakest CN strength have CN indices about 0.1 mag lower than those among the low-velocity disk field giants with the same UV excess.2. HIgh-velocity field giants of the same ultraviolet excess show similar CN strengths to those shown by the 47 Tuc giants.3. The giants in the metal poor disk clusters NGC 2420 and Melotte 66 exhibit the same CN behavior as the low-velocity disk giants.4. The CN strong giants in 47 Tuc show significantly lower ultraviolet excess (by approx.0.07 mag) than the CN weak stars.5. Although the CN strong stars in 47 Tuc define precisely the same giant sequences in the color-magnitude diagram as the weak CN stars, they are relatively more abundant on the asymptotic branch and near the tip of the giant branch.We conclude that the primeval nitrogen abundance we lower in the gas which formed the inner-halo stars than it was in the disk. We also conclude that the bimodal distribution in CN strength observed in 47 Tuc may be present in other stellar populations in varying degrees, and that therefore it is a normal aspect of stellar evolution.Finally, we propose an explanation for the second-parameter problem in halo clusters in which variations in nitrogen abundance play a key role.

• Research Organization: University of Victoria
• OSTI ID: 5536155
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 235:2; 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
ABUNDANCE
CHEMICAL COMPOSITION
CRYOGENIC FLUIDS
CYANOGEN
ELEMENTS
FLUIDS
GIANT STARS
NITROGEN
NONMETALS
PHOTOMETRY
STAR CLUSTERS
STAR EVOLUTION
STARS
VELOCITY