Ca II emission from old red giants in the globular cluster M15

Nature ◽  
1991 ◽  
Vol 354 (6351) ◽  
pp. 284-286
Author(s):  
A. K. Dupree ◽  
B. A. Whitney
Keyword(s):  
Globular Cluster ◽  
Red Giants

scholarly journals The Hertzsprung-Russell Diagram of Metal-Poor Disk Stars

1978 ◽  
Vol 80 ◽  
pp. 273-276
Author(s):  
Sidney van den Bergh
Keyword(s):  
Velocity Field ◽  
Globular Cluster ◽  
High Velocity ◽  
Population Model ◽  
Open Cluster ◽  
Ultraviolet Excess ◽  
Red Giants ◽  
The Sun ◽  
The Galaxy ◽  
Red Giant

A quarter of a century ago Keenan and Keller (1953) showed that the majority of high-velocity stars near the Sun outline a Hertzsprung-Russell diagram similar to that of old Population I. This result, which did not appear to fit into Baade's (1944) two-population model of the Galaxy was ignored (except by Roman 1965) for the next two decades. Striking confirmation of the results of Keenan and Keller was, however, obtained by Hartwick and Hesser (1972). Their work appears to show that high-velocity field stars with an ultraviolet excess (which measures Fe/H) of δ(U-B) ≃ +0m.11 lie on a red giant branch that is more than a magnitude fainter than the giant branch of the strong-lined globular cluster 47 Tuc for which δ(U-B) ≃ +0m.10. Furthermore Demarque and McClure (1977) show that the red giants in the old metal poor [δ(U-B) ≃ +0m.11] open cluster NGC 2420 are significantly fainter than are those in 47 Tuc. Calculations by these authors show that the observed differences between the giants in 47 Tuc and in NGC 2420 can be explained if either (1) 47 Tuc is richer in helium than NGC 2420 by ΔY ≃ 0.1 or (2) if 47 Tuc has a ten times lower value of Z(CNO) than does NGC 2420.

Stellar encounters involving red giants in globular cluster cores

1991 ◽  
Vol 381 ◽  
pp. 449 ◽  
Author(s):  
M. B. Davies ◽  
W. Benz ◽  
J. G. Hills
Keyword(s):  
Globular Cluster ◽  
Red Giants ◽  
Cluster Cores

scholarly journals A LARGE SAMPLE STUDY OF RED GIANTS IN THE GLOBULAR CLUSTER OMEGA CENTAURI (NGC 5139)

2009 ◽  
Vol 698 (2) ◽  
pp. 2048-2065 ◽  
Author(s):  
Christian I. Johnson ◽  
Catherine A. Pilachowski ◽  
R. Michael Rich ◽  
Jon P. Fulbright
Keyword(s):  
Globular Cluster ◽  
Red Giants ◽  
Large Sample

scholarly journals Photometry of the Globular Cluster NGC 5466: Red Giants and Blue Stragglers

2007 ◽  
Vol 663 (1) ◽  
pp. 277-295 ◽  
Author(s):  
Nassissie Fekadu ◽  
Eric L. Sandquist ◽  
Michael Bolte
Keyword(s):  
Globular Cluster ◽  
Red Giants ◽  
Blue Stragglers
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