Chemical composition of the old open clusters melotte 66 and NGC 2243

Journal Article · Tue Jun 15 00:00:00 EDT 1982 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/160020· OSTI ID:6940053

Gratton, R G

The chemical composition of the old open cluster Melotte 66 and NGC 2243 is determined by means of high-dispersion spectra of some red giants and a model atmosphere analysis. The two clusters are found to be quite metal poor ((Fe/H) = -0.7 +- 0.1 for Melotte 66 and (Fe/H) = -1.2 +- 0.1 for NGC 2243), with oxygen perhaps enhanced in NGC 2243. A reanalysis is made of the color-magnitude diagrams of the four old open clusters which have been studied with high dispersion (M67, NGC 2420, NGC 2243, and Melotte 66), and new values for the distance moduli of M67 and Melotte 66 are determined. Age estimates are 4 x 10/sup 9/ years for M67 and NGC 2420 and 6 x 10/sup 9/ years for NGC 2243 and Melotte 66. The helium content = 0.25 +- 0.03 is estimated from the magnitude of the horizontal branch and the ratio of the horizontal branch stars to red giants, and seems remarkably constant within this sample of clusters. The results suggest that the time scale of the galactic halo collapse is long (5--10 x 10/sup 9/ years), in agreement with recent models.

• Research Organization: Cerro Tololo Inter-American Observatory
• OSTI ID: 6940053
• Journal Information: Astrophys. J.; (United States), Vol. 257:2
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
STAR CLUSTERS
CHEMICAL COMPOSITION
ABUNDANCE
DATA ANALYSIS
HELIUM
RED GIANT STARS
SPECTRA
STAR EVOLUTION
STAR MODELS
STELLAR ATMOSPHERES
ATMOSPHERES
ELEMENTS
FLUIDS
GASES
GIANT STARS
MATHEMATICAL MODELS
NONMETALS
RARE GASES
STARS
640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar
Radio & X-Ray Sources