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 The Globular Cluster ω Centauri and its RR Lyrae Variables

1989 ◽  
Vol 111 ◽  
pp. 141-167
Author(s):  
R.J. Dickens
Keyword(s):  
Globular Cluster ◽  
Main Sequence ◽  
Red Giants ◽  
Horizontal Branch ◽  
Main Sequence Stars ◽  
Chemical Enrichment ◽  
Rr Lyrae ◽  
Stellar Pulsation ◽  
Stellar Ages ◽  
Period Shift

AbstractThe significance of some of the unusual characteristics of the globular cluster ω Centauri in various fundamental problems is explored. Interest is centred on the properties of the cluster RR Lyraes, and what they can contribute to studies of early cluster chemical enrichment, stellar pulsation, the distance scale, stellar evolution, stellar ages and the Oosterhoff period-shift problem. This article, which is intended to highlight problems and progress rather than give a comprehensive review, includes new results based on photometry of the RR Lyraes, red giants, subgiants, horizontal-branch and main sequence stars in the cluster.

scholarly journals Period Changes of RR Lyrae Stars in the LMC Globular Cluster NGC 2257

1984 ◽  
Vol 108 ◽  
pp. 39-40 ◽  
Author(s):  
James M. Nemec ◽  
Martha H. Liller ◽  
James E. Hesser
Keyword(s):  
Physical Properties ◽  
Globular Cluster ◽  
Period Change ◽  
Stellar Systems ◽  
Horizontal Branch ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Horizontal Branch Stars ◽  
Lyrae Stars

The period changes of RR Lyrae stars can be compared with models of horizontal branch stars as a means of investigating the physical properties of the stars themselves, and of the stellar systems in which they are found (Smith and Sandage 1981). The present study is the first in which period change rates of extragalactic RR Lyraes have been estimated.

scholarly journals THE ABUNDANCES OF NEUTRON-CAPTURE SPECIES IN THE VERY METAL-POOR GLOBULAR CLUSTER M15: A UNIFORM ANALYSIS OF RED GIANT BRANCH AND RED HORIZONTAL BRANCH STARS

2011 ◽  
Vol 141 (6) ◽  
pp. 175 ◽  
Author(s):  
Jennifer S. Sobeck ◽  
Robert P. Kraft ◽  
Christopher Sneden ◽  
George W. Preston ◽  
John J. Cowan ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Neutron Capture ◽  
Horizontal Branch ◽  
Horizontal Branch Stars ◽  
Red Giant

scholarly journals The Variable Stars in NGC 6723

1973 ◽  
Vol 21 ◽  
pp. 178-179
Author(s):  
John Menzies
Keyword(s):  
Southern Hemisphere ◽  
Globular Cluster ◽  
Variable Stars ◽  
Horizontal Branch ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Horizontal Branch Stars ◽  
Magnitude Diagram ◽  
The Mean ◽  
Lyrae Stars

Abstract*.A study has been made of the variables in the Southern Hemisphere globular cluster NGC 6723, which is suspected of being relatively metal-rich on the basis of its colour-magnitude diagram and of its integrated spectral type of G3. Seven new RR Lyrae stars and two bright red, probably semiregular, variables have been found and the suspected variable of Fourcade and Laborde has been confirmed. The complement of RR Lyrae stars is now 27, consisting of 4 c-type and 23 ab-type variables, the mean periods being Pc = 0.d292 and Pab = 0.d537. On the basis of the two-colour diagram of the horizontal branch stars the cluster is considered to be virtually un-reddened. Applying Christy’s models to the data from this study we find the following parameters for the variables: Mv= 1.m10, mass = 0.42 M⊙, and Y=0.4.

scholarly journals Precise radial velocities of giant stars

2020 ◽  
Vol 644 ◽  
pp. A1
Author(s):  
Marcelo Tala Pinto ◽  
Sabine Reffert ◽  
Andreas Quirrenbach ◽  
Stephan Stock ◽  
Trifon Trifonov ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Main Sequence ◽  
Evolutionary Stage ◽  
Horizontal Branch ◽  
Giant Stars ◽  
Horizontal Branch Stars ◽  
Formation And Evolution ◽  
Red Giant ◽  
Data Yield ◽  
Giant Branch Stars

Context. More than 100 exoplanets have been discovered around K and G giant stars, and their properties differ considerably from those of the planets found orbiting Sun-like and late-type main-sequence stars. This allows us to study the properties of planetary systems after the host star has evolved off the main-sequence, and it helps us to constrain planetary formation and evolution models. Aims. Our aim is to find out whether the long-period radial velocity variations observed in four giant stars of the Lick survey are caused by orbiting planets, and to study the properties of the planet population as a function of the stellar evolutionary stage. Methods. We analyzed 12 yr of precise radial velocity data for four stars of the Lick sample. In addition, we compared the planet frequency as a function of the evolutionary stage for two surveys, Lick and Express, based on the evolutionary stages derived using Bayesian inference. Results. We report the discovery of two new exoplanets and three exoplanet candidates orbiting giant stars. The best Keplerian fits to the data yield minimum masses of 2.5 MJ and 4.3 MJ for the planets orbiting HD 25723 and 17 Sco, respectively. The minimum masses of an additional candidate around HD 25723, and of planet candidates around 3 Cnc and 44 UMa, would be 1.3 MJ, 20.7 MJ, and 12.1 MJ, respectively. In addition, we compute planet frequencies for the Lick and Express samples as a function of the evolutionary stage. Within each sample, the planet frequency for the horizontal branch stars is the same as for the red giant branch stars. Conclusions. We have discovered two new exoplanets and three new exoplanet candidates, one of them being the second planet in a possible multi-planetary system. Based on our derived planet frequencies, we conclude that stellar evolution does not affect the number of observable planets between the red-giant and horizontal-branch evolutionary stages.

scholarly journals Are Galactic globular cluster AGB stars rich or poor in Sodium? Sodium abundance of AGB and RGB stars in NGC 2808

2015 ◽  
Vol 12 (S316) ◽  
pp. 361-362
Author(s):  
Yue Wang ◽  
Francesca Primas ◽  
Corinne Charbonnel ◽  
Mathieu Van der Swaelmen ◽  
William Chantereau ◽  
...  
Keyword(s):  
Spectroscopic Study ◽  
Globular Cluster ◽  
Main Sequence ◽  
Significant Fraction ◽  
Agb Stars ◽  
2Nd Generation ◽  
Red Giant ◽  
Sodium Abundance

AbstractA spectroscopic study comparing the [Na/Fe] distributions of RGB and AGB stars in the Galactic globular cluster (GC) NGC 6752 found that there was no Na-rich, 2nd-generation star along the early-AGB of this cluster. This came as a surprise since in this GC, as well as other Galactic GCs studied so far, 1st- and 2nd-generation stars have usually been found from the main sequence turnoff up to the red giant branch. To investigate whether the failure of a significant fraction of stars to ascend the AGB also happens to other GCs, we studied a sample of AGB and RGB stars in NGC 2808 observed at the ESO/VLT with FLAMES. Contrary to NGC 6752, we find that the AGB and RGB stars we studied in NGC 2808 have comparable [Na/Fe] dispersions.

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 On the Interpretation of RR Lyrae Properties in Globular Clusters and in Other Population II Systems

1973 ◽  
Vol 21 ◽  
pp. 197-206
Author(s):  
V. Castellani ◽  
P. Giannone ◽  
A. Renzini
Keyword(s):  
Mass Loss ◽  
Globular Clusters ◽  
Horizontal Branch ◽  
Rr Lyrae ◽  
Horizontal Branch Stars

AbstractThe differences in observational parameters of the RR Lyrae variables and horizontal branch stars of globular clusters and other population II systems are considered. A discontinuous behaviour of some parameters is outlined. The Oosterhoff dichotomy and the HB morphology are discussed with regard to a conjecture of mass loss in the pre-HB phase.

scholarly journals The HST large programme on NGC 6752 – III. Detection of the peak of the white dwarf luminosity function

2019 ◽  
Vol 488 (3) ◽  
pp. 3857-3865
Author(s):  
L R Bedin ◽  
M Salaris ◽  
J Anderson ◽  
M Libralato ◽  
D Apai ◽  
...  
Keyword(s):  
Globular Cluster ◽  
White Dwarf ◽  
Luminosity Function ◽  
Main Sequence ◽  
Hubble Space Telescope ◽  
Horizontal Branch ◽  
Space Telescope

ABSTRACT We report on the white dwarf (WD) cooling sequence of the old globular cluster NGC 6752, which is chemically complex and hosts a blue horizontal branch. This is one of the last globular cluster WD cooling sequences accessible to imaging by the Hubble Space Telescope. Our photometry and completeness tests show that we have reached the peak of the luminosity function of the WD cooling sequence, at a magnitude mF606W  = 29.4 ± 0.1, which is consistent with a formal age of ∼14 Gyr. This age is also consistent with the age from fits to the main-sequence turn-off (13–14 Gyr), reinforcing our conclusion that we observe the expected accumulation of WDs along the cooling sequence.

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