Spread in CO absorption and effective temperature among the giants in omega Centauri

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

DOI:https://doi.org/10.1086/157648· OSTI ID:5662188

Persson, S E; Frogel, J A; Cohen, J G; Aaronson, M; Matthews, K

Infrared photometric observations of 82 stars on the upper giant branch of ..omega.. Centauri are presented. The data show that ..omega.. Cen differs markedly from other globular clusters studied in the infrared in two respects. First, at a given V--K color, there is a wide spread in CO absorption (> or approx. =0.1 mag) in the 3 mag interval below the red giant tip; this range is approximately 5 times that found for other clusters. Second, at a given luminosity, V--K has a spread of up to 1 mag; this range is also much larger than that found for other cluster. The latter result leads us to conclude, in agreement with recent findings by other authors, that there are star-to-star variations in heavy-metal abundance within ..omega.. Cen of a factor of 30 or more.Comparison of the spread in CO absorption with that in V -- K reveals two sequences of stars, one which has ''enhanced'' CO absorption and one which has ''normal'' CO absorption when compared to the run of CO with V--K among stars in other globular clusters. The proportion of stars having ''enhanced'' CO exceeds 50%. Many of the strong CN stars in the cluster also have ''enhanced'' CO. Explanations for the orign of these sequences which involve primordial abundance variations as well as mixing phenomena are discussed briefly. Implications for the identification of the ''second parameter'' as the CNO abundance are also discussed.Effective temperatures and bolometric luminosities are given for the stars.

• Research Organization: Hale Observatories, Carnegie Institution of Washington
• OSTI ID: 5662188
• 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
ABSORPTION
ABUNDANCE
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL COMPOSITION
CHEMISTRY
COSMOCHEMISTRY
GIANT STARS
INFRARED SPECTRA
LUMINOSITY
OPTICAL PROPERTIES
OXIDES
OXYGEN COMPOUNDS
PHOTOMETRY
PHYSICAL PROPERTIES
SPECTRA
STAR CLUSTERS
STAR EVOLUTION
STARS