scholarly journals Striking Photospheric Abundance Anomalies in Blue Horizontal-Branch Stars in Globular Cluster M13

1999 ◽  
Vol 517 (2) ◽  
pp. L135-L138 ◽  
Author(s):  
Bradford B. Behr ◽  
Judith G. Cohen ◽  
James K. McCarthy ◽  
S. George Djorgovski
Keyword(s):  
Globular Cluster ◽  
Horizontal Branch ◽  
Horizontal Branch Stars ◽  
Abundance Anomalies

Abundance anomalies in hot horizontal-branch stars of the globular cluster NGC 6752

1989 ◽  
Vol 339 ◽  
pp. 926 ◽  
Author(s):  
J. W. Glaspey ◽  
G. Michaud ◽  
A. F. J. Moffat ◽  
S. Demers
Keyword(s):  
Globular Cluster ◽  
Horizontal Branch ◽  
Horizontal Branch Stars ◽  
Abundance Anomalies

scholarly journals Abundance anomalies in hot horizontal branch stars of the galactic globular cluster NGC 1904

2005 ◽  
Vol 434 (1) ◽  
pp. 235-245 ◽  
Author(s):  
D. Fabbian ◽  
A. Recio-Blanco ◽  
R. G. Gratton ◽  
G. Piotto
Keyword(s):  
Globular Cluster ◽  
Horizontal Branch ◽  
Horizontal Branch Stars ◽  
Abundance Anomalies

Supra–Horizontal‐Branch Stars and Population Gradients in the Galactic Center Globular Cluster NGC 6522

1998 ◽  
Vol 495 (2) ◽  
pp. 796-803 ◽  
Author(s):  
M. M. Shara ◽  
L. Drissen ◽  
R. M. Rich ◽  
F. Paresce ◽  
I. R. King ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Galactic Center ◽  
Horizontal Branch ◽  
Horizontal Branch Stars

scholarly journals Particle Transport in Non-Magnetic Stars

1986 ◽  
Vol 90 ◽  
pp. 459-472
Author(s):  
G. Michaud
Keyword(s):  
Simple Model ◽  
Mass Loss ◽  
Large Fraction ◽  
Arbitrary Parameter ◽  
Horizontal Branch ◽  
Horizontal Branch Stars ◽  
Free Model ◽  
Magnetic Stars ◽  
Abundance Anomalies ◽  
F Stars

AbstractThe observations of AmFm, λ Booti, HgMn and He rich stars that are explained without any arbitrary parameter by diffusion are briefly reviewed, followed by those observations that are not explained by this simple model. Mass loss is then shown to explain a large fraction of the observations that are not explained in the parameter free model. It seems to play a role in the λ Booti, AmFm, He rich and the hot horizontal branch stars. It is only of about 10−15 to 10−13 Mo/yr. Abundance anomalies then help to determine stellar hydrodynamics. It is finally suggested that recent observations of Li underabundances in F stars of the Hyades represent an extension of the AmFm star phenomenon.

scholarly journals The Influence of Rotation on Horizontal Branch Stars and on RR Lyrae Pulsational Properties

1981 ◽  
Vol 93 ◽  
pp. 275-275
Author(s):  
V. Castellani
Keyword(s):  
Globular Cluster ◽  
Main Sequence ◽  
Horizontal Branch ◽  
Structural Variations ◽  
Rr Lyrae ◽  
Horizontal Branch Stars ◽  
Mass Size ◽  
Red Giant

The occurrence of rotation in Globular Cluster stars has been suggested (see e.g. Renzini 1977) as a mechanism producing the observed colour spread in actual Horizontal Branches. If this is the case, canonical results on evolutionary properties of HB stars have to be revisited in order to account for rotation-driven structural variations: faster Main Sequence rotators delay the He flash increasing the mass-size Mc of the He core at the flash and loosing a greater amount of mass during the Red Giant stage.

scholarly journals Pal 1: A Globular Cluster Anyway?

1995 ◽  
Vol 164 ◽  
pp. 395-395
Author(s):  
J. Borissova ◽  
N. Spassova
Keyword(s):  
Globular Cluster ◽  
Luminosity Function ◽  
Main Sequence ◽  
Structural Parameters ◽  
Distance Modulus ◽  
Horizontal Branch ◽  
Ccd Photometry ◽  
Horizontal Branch Stars ◽  
Mass Estimate

CCD photometry of the halo cluster Pall in Thuan-Gunn system is presented. The color - magnitude diagrams (Fig. 1) show a well defined red horizontal branch, lower giant branch and main-sequence down to about two magnitudes below the main-sequence turnoff. The giant branch is absent and the brightest stars are horizontal-branch stars. The horizontal branch is composed of red stars only. The age of the cluster, determined by comparison with the isochrones of Bell and Vanden Berg (1987) is consistent with an age between 12 – 14 Gyr. and a metallicity [Fe/H] = −0.79. The observed luminosity function shows a deficiency of stars from about 0.5 mag below turnoff up to g = 21 mag. A distance modulus of (m – M)g0 = 15.35 ± 0.1 magnitude has been derived. An estimate of the cluster structural parameters gives rc = 1.7 pc and c = 1.46. A mass estimate of 1.6 × 103M⊙ and mass-to-light ratio 1.77 has been obtained, using King's (1966) method.

scholarly journals AstroSat Study of the Globular Cluster NGC 2298: Probable Evolutionary Scenarios of Hot Horizontal Branch Stars

2021 ◽  
Vol 923 (2) ◽  
pp. 162
Author(s):  
Sharmila Rani ◽  
Gajendra Pandey ◽  
Annapurni Subramaniam ◽  
Chul Chung ◽  
Snehalata Sahu ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Hubble Space Telescope ◽  
Spectral Energy Distribution ◽  
Outer Region ◽  
Spectral Energy ◽  
Horizontal Branch ◽  
Horizontal Branch Stars ◽  
Cooling Phase ◽  
Ehb Stars ◽  
Optical Color

Abstract We present the far-UV (FUV) photometry of images acquired with UVIT on AstroSat to probe the horizontal branch (HB) population of the Galactic globular cluster NGC 2298. UV-optical color–magnitude diagrams (CMDs) are constructed for member stars in combination with Hubble Space Telescope UV Globular Cluster Survey data for the central region and Gaia and ground-based photometric data for the outer region. A blue HB (BHB) sequence with a spread and four hot HB stars are detected in all FUV-optical CMDs and are compared with theoretical updated BaSTI isochrones and synthetic HB models with a range in helium abundance, suggesting that the hot HB stars are helium enhanced when compared to the BHB. The estimated effective temperature, radius, and luminosity of HB stars, using the best spectral energy distribution fits, were compared with various HB models. BHB stars span a temperature range from 7500 to 12,250 K. Three hot HB stars have 35,000–40,000 K, whereas one star has around ∼100,000 K. We suggest the following evolutionary scenarios: two stars are likely to be the progeny of extreme HB (EHB) stars formed through an early hot-flasher scenario, one is likely to be an EHB star with probable helium enrichment, and the hottest HB star, which is about to enter the white dwarf cooling phase, could have evolved from the BHB phase. Nevertheless, these are interesting spectroscopic targets to understand the late stages of evolution.

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