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Elektronische Textkommunikation in Deutschland und Japan / Electronic Text Communication in Germany and Japan - Konzepte, Anwendungen, Soziale Wirkungen, Einfuhrungsstrategien / Concepts, Applications, Social Impacts, Implementation Strategies (Paperback, Softcover reprint of the original 1st ed. 1984)
A Chimiak, R.C. Hider, A Liu, J.B. Neilands, K. Nomoto, …
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R2,953
Discovery Miles 29 530
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Ships in 10 - 15 working days
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The open cluster NGC 6791 is now considered both the oldest and the
most metal-rich known. Its age is 8 -10 Gyrs, twice as old as the
canonical solar-metallicity cluster M67 (Garnavich et al. 1994;
Demarque, Green, & Guenther 1992; Tripicco et al. 1995). That
its metallicity is significantly above solar is suggested from
moderate-resolution spectroscopy and from a mismatch of its
color-magnitude diagram (CMD) with solar-metallicity isochrones.
Tripicco et al. (1995) find [Fe/H] = +0.27 to +0.44. The cluster
population is rich. In addition to about a dozen red giants and two
dozen red horizontal-branch stars, the cluster has several very hot
HB stars (Kaluzny & Udalski 1992). Liebert et al. (1994) have
shown that the extremely blue stars are mostly sdB/sdO stars and at
least 3 or 4 are likely cluster members, the first ever discovered
in an open cluster. These may provide the key to the puzzling
upturn in ultraviolet flux below 1500A seen in many
high-metallicity systems (Burstein et al. 1988; Ferguson et al.
& Liebert 1993).
The open cluster NGC 6791 is now considered both the oldest and the
most metal-rich known. Its age is 8 -10 Gyrs, twice as old as the
canonical solar-metallicity cluster M67 (Garnavich et al. 1994;
Demarque, Green, & Guenther 1992; Tripicco et al. 1995). That
its metallicity is significantly above solar is suggested from
moderate-resolution spectroscopy and from a mismatch of its
color-magnitude diagram (CMD) with solar-metallicity isochrones.
Tripicco et al. (1995) find [Fe/H] = +0.27 to +0.44. The cluster
population is rich. In addition to about a dozen red giants and two
dozen red horizontal-branch stars, the cluster has several very hot
HB stars (Kaluzny & Udalski 1992). Liebert et al. (1994) have
shown that the extremely blue stars are mostly sdB/sdO stars and at
least 3 or 4 are likely cluster members, the first ever discovered
in an open cluster. These may provide the key to the puzzling
upturn in ultraviolet flux below 1500A seen in many
high-metallicity systems (Burstein et al. 1988; Ferguson et al.
& Liebert 1993).
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