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

Abstract

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.

Authors:
Publication Date:
Research Org.:
Cerro Tololo Inter-American Observatory
OSTI Identifier:
6940053
Resource Type:
Journal Article
Journal Name:
Astrophys. J.; (United States)
Additional Journal Information:
Journal Volume: 257:2
Country of Publication:
United States
Language:
English
Subject:
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

Citation Formats

Gratton, R G. Chemical composition of the old open clusters melotte 66 and NGC 2243. United States: N. p., 1982. Web. doi:10.1086/160020.
Gratton, R G. Chemical composition of the old open clusters melotte 66 and NGC 2243. United States. https://doi.org/10.1086/160020
Gratton, R G. 1982. "Chemical composition of the old open clusters melotte 66 and NGC 2243". United States. https://doi.org/10.1086/160020.
@article{osti_6940053,
title = {Chemical composition of the old open clusters melotte 66 and NGC 2243},
author = {Gratton, R G},
abstractNote = {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.},
doi = {10.1086/160020},
url = {https://www.osti.gov/biblio/6940053}, journal = {Astrophys. J.; (United States)},
number = ,
volume = 257:2,
place = {United States},
year = {Tue Jun 15 00:00:00 EDT 1982},
month = {Tue Jun 15 00:00:00 EDT 1982}
}