scholarly journals Faint CCD photometry in globular clusters. II. Comparison of theoretical isochrones with the globular clusters M4 and M15

1984 ◽  
Vol 105 ◽  
pp. 147-151
Author(s):  
Harvey B. Richer ◽  
G.G. Fahlman
Keyword(s):  
Early Universe ◽  
Stellar Evolution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Formation Time ◽  
Chemical Inhomogeneity ◽  
Ccd Photometry ◽  
Testing Ground ◽  
Astronomical Research

Globular cluster work touches on virtually all branches of astronomical research. The age of the globular system (or any variations in age among individual clusters) has important cosmological implications as well as relating to the formation time of the halo of our galaxy. Star to star chemical inhomogeneity within a cluster may set important constraints on either mixing within the stars themselves or on the chemical inhomogeneity of the early universe. Metallicity variations among clusters may provide the clue to galaxy-wide enrichment processes, while the cluster color-magnitude diagrams themselves are a testing ground for virtually every facet of stellar evolution.

scholarly journals Dynamical Evolution of Rotating Globular Clusters

1996 ◽  
Vol 174 ◽  
pp. 375-376
Author(s):  
P.-Y. Longaretti ◽  
C. Lagoute
Keyword(s):  
Angular Momentum ◽  
Stellar Evolution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Dynamical Evolution

We have computed simplified globular cluster evolutionary tracks which take into account the effects of internal relaxation, of the cluster rotation, of the galactic tidal field, and, in a cruder way, of stellar evolution and of gravitational shocking. The objectives are first to quantify the influence of rotation in the dynamical evolution of globular clusters; and second, to investigate the evolution of globular cluster angular momentum and flattening (Lagoute and Longaretti 1995a, Longaretti and Lagoute 1995b,c).

scholarly journals CCD Observations of Variable Stars in Globular Clusters

1989 ◽  
Vol 111 ◽  
pp. 285-285
Author(s):  
H.A. Smith ◽  
J.R. Kuhn ◽  
J. Curtis
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Variable Stars ◽  
Michigan State University ◽  
State University ◽  
Ccd Photometry ◽  
Rr Lyrae ◽  
Short Period ◽  
Ccd Observations ◽  
Period Variable

AbstractBVR observations of the relatively metal-rich globular cluster NGC 6388 have been obtained with a CCD on the CTIO 0.9 m telescope. Eighteen possible short period variable stars have been discovered in or near the cluster. At least 10 of these are probable RR Lyrae members of NGC 6388. We confirm the finding of Hazen and Hesser that this cluster is one of the most metal-rich to contain a significant number of RR Lyraes. A program of CCD photometry of field and cluster variable stars has been initiated on the 0.6m telescope of the Michigan State University Observatory.

scholarly journals Double-radial-mode SX Phoenicis stars in the globular clusters NGC 5466 and M71

2004 ◽  
Vol 193 ◽  
pp. 166-170
Author(s):  
Young-Beom Jeon ◽  
Myung Gyoon Lee ◽  
Seung-Lee Kim ◽  
Ho Lee
Keyword(s):  
Time Series ◽  
Globular Cluster ◽  
Fundamental Mode ◽  
Globular Clusters ◽  
Radial Mode ◽  
Ccd Photometry ◽  
Period Ratio

AbstractThrough time-series CCD photometry of the globular cluster NGC 5466, we found three double-radial-mode SX Phe stars, all of which are consistent with the theoretical period ratio of the first overtone mode to the fundamental mode (P1H/PF); their period ratios are 0.7825, 0.7826 and 0.7919, respectively. We also detected a double-radial-mode SX Phe star in M71. Its period ratio is 0.781, which is also consistent with the theoretical value.

scholarly journals Cluster Mass and Metallicity Distributions: Reconstructing the Events During Halo Formation

2002 ◽  
Vol 207 ◽  
pp. 545-554
Author(s):  
William E. Harris
Keyword(s):  
Star Formation ◽  
Mass Distribution ◽  
Early Universe ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Potential Wells ◽  
Cluster Mass ◽  
Galactic Potential ◽  
Initial Power ◽  
Lines Of Evidence

Globular clusters in most large galaxies are a mixture of metal-poor and metal-rich (bimodal), but the halo stars are almost entirely metal-rich. This and other lines of evidence argue that the metal-poor globular clusters formed within widely distributed 108 − 109M⊙ gas clouds (supergiant GMCs) during an early burst in which most of the gas was ejected or unused till later rounds of star formation.New simulations of the growth of pre-galactic potential wells in the early universe now indicate that the initial power-law form of the globular cluster mass distribution (dN/dM ∼ M-1.8) is a miniature replica of the mass distribution of the SGMCs themselves, which grow hierarchically in the CDM potential wells of large protogalaxies.

scholarly journals Globular cluster ages from main sequence fitting and detached, eclipsing binaries: The case of 47 Tuc

2008 ◽  
Vol 4 (S258) ◽  
pp. 171-176 ◽  
Author(s):  
Aaron Dotter ◽  
Janusz Kaluzny ◽  
Ian B. Thompson
Keyword(s):  
Stellar Evolution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Main Sequence ◽  
Eclipsing Binaries ◽  
Eclipsing Binary ◽  
Age Constraints

AbstractAge constraints are most often placed on globular clusters by comparing their CMDs with theoretical isochrones. The recent discoveries of detached, eclipsing binaries in such systems by the Cluster AgeS Experiment (CASE) provide new insights into their ages and, at the same time, provide much-needed tests of stellar evolution models. We describe efforts to model the properties of the detached, eclipsing binary V69 in 47 Tuc and compare age constraints derived from stellar evolution models of V69A and B with ages obtained from fitting isochrones to the cluster CMD. We determine whether or not, under reasonable assumptions of distance, reddening, and metallicity, it is possible to simultaneously constrain the age and He content of 47 Tuc.

The relationship between globular cluster parameters and abundance variations

2019 ◽  
Vol 14 (S351) ◽  
pp. 333-336
Author(s):  
David M. Nataf
Keyword(s):  
Early Universe ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Meta Analysis ◽  
Stellar Mass ◽  
Prior Literature ◽  
Nitrogen Abundance ◽  
Using Data ◽  
Sodium Abundance ◽  
The Relationship

AbstractWe discuss a meta-analysis of the association of abundance variations in globular cluster stars with the present-day stellar mass and metallicity of globular clusters. Using data for 42 globular clusters that are well-sampled from either or both of prior literature studies and the APOGEE survey, we confirm prior findings that increasing aluminum abundance variations in globular clusters are positively correlated with increasing present-day stellar mass or decreasing metallicity. We also demonstrate that the ratio of aluminum abundance variations to either nitrogen abundance variations or sodium abundance variations is itself positively correlated with decreasing metallicity and increasing stellar mass of globular clusters. This suggests that there were at least two non-supernovae chemical polluters that were active in the early universe.

scholarly journals Coulomb Corrections and Globular Cluster Stellar Evolution

1993 ◽  
Vol 137 ◽  
pp. 451-453 ◽  
Author(s):  
Charles R. Proffitt
Keyword(s):  
Equation Of State ◽  
Stellar Evolution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Main Sequence ◽  
Stellar Interior ◽  
Coulomb Effects

AbstractThe effects of Coulomb corrections on the evolution of globular clusters stars are discussed. Coulomb corrections alter the equation of state by about 1% in most of the stellar interior, and for stars of fixed initial parameters, this results in an 8% increase in the ZAMS luminosity and an 8% decrease in the age at the main sequence turnoff. Ages for globular clusters measured by comparing to the turnoff luminosity of theoretical isochrones are lowered by ≈ 4% when Coulomb effects are included.

scholarly journals Dynamical Evolution of the Mass Function of the Globular Cluster System from Fokker-Planck Calculations: Preliminary Results

2006 ◽  
Vol 2 (S235) ◽  
pp. 110-110
Author(s):  
Jihye Shin ◽  
Sungsoo S. Kim
Keyword(s):  
Stellar Evolution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Dynamical Evolution ◽  
Mass Function ◽  
Cluster System ◽  
Dynamical Friction ◽  
Luminosity Functions ◽  
Globular Cluster System ◽  
Fokker Planck

AbstractUsing anisotropic Fokker-Planck models, we calculate the evolution of mass and luminosity functions of the Galactic globular cluster system. Our models include two-body relaxation, binary heating, tidal shocks, dynamical friction, and stellar evolution. We perform Fokker-Planck simulations for a large number of virtual globular clusters and synthesize these results to study the relation between the initial and present GCMFs.

scholarly journals An extremely metal-deficient globular cluster in the Andromeda Galaxy

Science ◽  
2020 ◽  
Vol 370 (6519) ◽  
pp. 970-973
Author(s):  
Søren S. Larsen ◽  
Aaron J. Romanowsky ◽  
Jean P. Brodie ◽  
Asher Wasserman
Keyword(s):  
Early Universe ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Chemical Elements ◽  
Heavy Elements ◽  
The Sun ◽  
Andromeda Galaxy ◽  
Iron Abundance

Globular clusters (GCs) are dense, gravitationally bound systems of thousands to millions of stars. They are preferentially associated with the oldest components of galaxies, so measurements of their composition can constrain the build-up of chemical elements in galaxies during the early Universe. We report a massive GC in the Andromeda Galaxy (M31), RBC EXT8, that is extremely depleted in heavy elements. Its iron abundance is about 1/800 that of the Sun and about one-third that of the most iron-poor GCs previously known. It is also strongly depleted in magnesium. These measurements challenge the notion of a metallicity floor for GCs and theoretical expectations that massive GCs could not have formed at such low metallicities.

scholarly journals The Chemical Inhomogeneity within Globular Clusters

1988 ◽  
Vol 126 ◽  
pp. 93-106
Author(s):  
John Norris
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Binary Systems ◽  
Chemical Inhomogeneity ◽  
Low Mass Stars ◽  
Stellar Collisions ◽  
Low Mass ◽  
Abundance Anomalies ◽  
Insight Into ◽  
The Way

Twenty years ago it was believed by most astronomers that globular clusters were chemically homogeneous - where by homogeneous one means that the outer layers of all stars within a given cluster are the same to within a few tens of percent. Today it is possible to defend the case that no Galactic globular cluster has this characteristic. The reason that this phenomenon has exercised the minds of so many groups in the past 15 years is exciting and obvious: if one can ascertain which are the relevant physical processes in operation, one stands to gain significant insight into both the way in which globular clusters formed and/or the way in which individual low mass stars evolve and mix the products of their nucleosynthesis into their outer layers. A second important driver at the back of the minds of workers in this field is the possible ramifications of an understanding of the phenomenon; for example, if one concludes that the abundance anomalies are being driven today by some particular effect (angular momentum, magnetic fields, interactions within binary systems, stellar collisions - or whatever) this may lead to insight into other important globular cluster phenomena (eg bimodal horizontal branches, gaps at the base of the giant branch, horizontal branch rotation, etc.)

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