scholarly journals A Photoelectric Investigation of the Eclipsing Binary V 78 in Omega Centauri (NGC 5139)

1971 ◽  
Vol 15 ◽  
pp. 235-237
Author(s):  
Edward H. Geyer
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Variable Star ◽  
Eclipsing Binaries ◽  
Stellar Systems ◽  
Light Elements ◽  
Eclipsing Binary ◽  
Evolved Stars ◽  
Photographic Photometry ◽  
Highly Evolved

The existence of eclipsing binaries, though extremely rare, in stellar systems like globular clusters, should attract the observers, because one could obtain fundamental data on highly evolved stars. The variable star V 78 in the globular cluster NGC 5139, which was found by BAILEY (1901), is one of these rare cases. MARTIN (1938) derived the period P = 1ḍ168118, and showed by means of an extensive photographic photometry that it is an Algol type eclipsing binary. Recently SISTERO et al. (1968, 1969) rediscussed the observations of MARTIN, and with additional measurements derived the following light elements:

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.

scholarly journals Close Binary Systems in Globular Clusters: A Preliminary Report

1980 ◽  
Vol 88 ◽  
pp. 561-565 ◽  
Author(s):  
R. F. Webbink
Keyword(s):  
Globular Cluster ◽  
Preliminary Report ◽  
Globular Clusters ◽  
Binary Systems ◽  
Cataclysmic Variables ◽  
Eclipsing Binaries ◽  
Close Binary ◽  
Promising Candidate ◽  
Eclipsing Binary ◽  
Ursa Minor

A brief survey of known eclipsing binaries and cataclysmic variables in globular cluster fields is presented. None of the 47 known or suspected eclipsing variables is a promising candidate, although a very few remain possible members. V101 in M5 is a good candidate for membership, among 5 known or suspected dwarf novae. Three novae have been discovered in globular cluster fields, of which two are almost certainly members. Attention is also called to the eclipsing binary V80, a system which appears to contain an RRc variable, in the dwarf spheroidal galaxy in Ursa Minor.

scholarly journals Chemical abundances in tidally disrupted globular clusters

2009 ◽  
Vol 5 (S266) ◽  
pp. 157-160
Author(s):  
D. Yong ◽  
J. Meléndez ◽  
K. Cunha ◽  
A. I. Karakas ◽  
J. E. Norris ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Preliminary Analysis ◽  
Globular Clusters ◽  
Building Blocks ◽  
Light Elements ◽  
Chemical Abundances ◽  
Chemical Enrichment ◽  
Abundance Variation

AbstractWe present abundance measurements in the tidally disrupted globular cluster NGC 6712. In this cluster, there are large star-to-star variations of the light elements C, N, O, F and Na. While such abundance variations are seen in every well-studied globular cluster, they are not found in field stars and indicate that clusters like NGC 6712 cannot provide many field stars and/or field stars do not form in environments with chemical-enrichment histories like those of NGC 6712. Preliminary analysis of NGC 5466, another tidally disrupted cluster, suggests little (if any) abundance variation for O and Na and the abundance ratios [X/Fe] are comparable to field stars at the same metallicity. Therefore, globular clusters like NGC 5466 may have been Galactic building blocks.

scholarly journals A Search for Main-Sequence Binaries in Globular Clusters

1980 ◽  
Vol 85 ◽  
pp. 357-359 ◽  
Author(s):  
Martha H. Liller
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Eclipsing Binaries ◽  
Cluster Center ◽  
Distance Modulus ◽  
List Type ◽  
Galactic Latitude ◽  
Plate Material ◽  
Evolved Stars ◽  
Visual Distance

It is becoming increasingly clear that no (or only one or two) binaries occur among the evolved stars in globular clusters. Therefore, if binaries exist at all in these systems, they must be found on or near the main sequence. I have chosen 6 clusters to search for faint eclipsing binaries by the following criteria: (1)the apparent visual distance modulus (Harris 1976) (m-M)V ≤ 14.5 mag;(2)the Peterson and King (1975) concentration class c ≤ 1.5, so that the search can be conducted near or at the cluster center where binaries would most likely be found; and(3)the galactic latitude is sufficiently large to avoid problems of extreme contamination by field stars. The clusters thus chosen are NGC3201, 5139 (Omega Cen), 6121 (M4), 6218 (M12), 6254 (M10), and 6809 (M55). The plate material obtained on three nights with the 4-m telescope at CTIO in 1979, consists of seven to nine plates of each cluster on IIIa-F emulsion with an RG610 filter; the search is being conducted with a blink microscope.

The eye of Gaia on globular cluster kinematics: Internal rotation

2019 ◽  
Vol 14 (S351) ◽  
pp. 516-519
Author(s):  
A. Sollima ◽  
H. Baumgardt ◽  
M. Hilker
Keyword(s):  
Internal Rotation ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Stellar Systems ◽  
Large Sample ◽  
Data Release ◽  
Extensive Collection ◽  
Formation And Evolution ◽  
The Impact ◽  
Insight Into

AbstractI present the results of a survey of the kinematics of a large sample of Galactic globular clusters performed thanks to the synergy between the 2nd Gaia data release and the most extensive collection of radial velocities. This unprecedented dataset of 3D velocities of thousand of stars in 62 globular clusters has been used to investigate the rotation patterns of these stellar systems providing insight into the impact of two-body relaxation and tides on the formation and evolution of their rotation.

scholarly journals The Main Sequence of the Very Old Globular Cluster NGC 6397

1980 ◽  
Vol 85 ◽  
pp. 423-423
Author(s):  
Gonzalo Alcaino ◽  
William Liller
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Main Sequence ◽  
Narrow Range ◽  
Age Determination ◽  
The Sun ◽  
Age Of The Universe ◽  
The Universe ◽  
Photographic Photometry ◽  
Collapse Phase

We present photographic photometry for 1135 stars in the globular cluster NGC 6397, which, at a distance of 2.4 kpc, is most likely the second nearest globular to the Sun. The Racine wedge with the CTIO Yale 1 m telescope (Δm=3. 60 mag), the CTIO 4 m telescope (Δm=6. 83 mag) and the ESO 3.6 m telescope (Δm=3. 87 mag) was used to extend the photoelectric calibration from V≃16.1 to V≃20.7. The main sequence turnoff at V=16.7 and B-V=0.52 with respectively Mv =4.30 and (B-V)o =0.36 yields (m-M)v=12.40 and E(B-V)=0.16. Using the models of Iben and Rood (1970) and the isochrones of Demarque and McClure (1977), we deduce the cluster's age to be 17 × 109 years. This makes this object the oldest of the nine globular clusters with age determination and gives a lower limit to the age of the universe, rendering Ho ≤ 57 km sec−1 Mpc−1 if qo ≥ 0 is assumed. The large age spread of 6 billion years between NGC 6397 and 47 Tuc (the youngest counterpart with age data) indicates both that the protogalaxy underwent a slow collapse phase and that the abundances in globular clusters are lower for the oldest. The fact that the galactocentric distances for these clusters have the narrow range of 6 <R < 13 kpc makes it highly important to secure age data for extremely metal poor globulars far out in the halo.

scholarly journals Searching for globular cluster chemical anomalies on the main sequence of a young massive cluster

2020 ◽  
Vol 495 (1) ◽  
pp. 375-382 ◽  
Author(s):  
I Cabrera-Ziri ◽  
J S Speagle ◽  
E Dalessandro ◽  
C Usher ◽  
N Bastian ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Main Sequence ◽  
Mass Range ◽  
Light Elements ◽  
Chemical Anomalies ◽  
Global Parameters ◽  
Massive Cluster

ABSTRACT The spectroscopic and photometric signals of the star-to-star abundance variations found in globular clusters seem to be correlated with global parameters like the cluster’s metallicity, mass, and age. Understanding this behaviour could bring us closer to the origin of these intriguing abundance spreads. In this work we use deep HST photometry to look for evidence of abundance variations in the main sequence of a young massive cluster NGC 419 (∼105 M⊙, ∼1.4 Gyr). Unlike previous studies, here we focus on stars in the same mass range found in old globulars (∼0.75–1 M⊙), where light elements variations are detected. We find no evidence for N abundance variations among these stars in the Un − B and U − B colour–magnitude diagrams of NGC 419. This is at odds with the N variations found in old globulars like 47 Tuc, NGC 6352, and NGC 6637 with similar metallicity to NGC 419. Although the signature of the abundance variations characteristic of old globulars appears to be significantly smaller or absent in this young cluster, we cannot conclude if this effect is mainly driven by its age or its mass.

Globular Cluster — Bulge connection: Population synthesis models with multiple populations

2019 ◽  
Vol 14 (S351) ◽  
pp. 277-280
Author(s):  
Chul Chung ◽  
Young-Wook Lee ◽  
Dongwook Lim ◽  
Seungsoo Hong ◽  
Jenny J. Kim ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Milky Way ◽  
Light Elements ◽  
Population Synthesis ◽  
Early Type ◽  
Galactic Bulge ◽  
Individual Variations ◽  
New Treatments ◽  
The Universe

AbstractRecent analyses of Lee et al. (2018, 2019) have confirmed that Galactic bulge consists of stellar populations originated from Milky Way globular clusters (MWGCs). Motivated by this, here we present the evolutionary population synthesis (EPS) for the Galactic bulge and early-type galaxies (ETGs) with the realistic treatment of individual variations in light elements observed in the MWGCs. We have utilized our model with GC-origin populations to explain the CN spread observed in ETGs, and the results show remarkable matches with the observations. We further employ our model to estimate the age of ETGs, which are considered as good analogs for the MW bulge. We find that, without the effect of our new treatments, EPS models will almost always underestimate the true age of ETGs. Our analysis indicates that the EPS with GC-origin populations is an essential constraint in determining the ETG formation epoch and is closely related to understanding the evolution of the Universe.

scholarly journals A 2 day orbital period for a redback millisecond pulsar candidate in the globular cluster NGC 6397

2021 ◽  
Author(s):  
Manuel Pichardo Marcano ◽  
L E Rivera Sandoval ◽  
Thomas J Maccarone ◽  
Yue Zhao ◽  
Craig O Heinke
Keyword(s):  
Globular Cluster ◽  
Orbital Period ◽  
Globular Clusters ◽  
Variable Star ◽  
Optical Modulation ◽  
Optical Variability ◽  
Millisecond Pulsar ◽  
X Ray ◽  
Strong Candidate ◽  
Pulsar Searches

Abstract We report optical modulation of the companion to the X-ray source U18 in the globular cluster NGC 6397. U18, with combined evidence from radio and X-ray measurements, is a strong candidate as the second redback in this cluster, initially missed in pulsar searches. This object is a bright variable star with an anomalous red colour and optical variability (∼0.2 mag in amplitude) with a periodicity ∼1.96 days that can be interpreted as the orbital period. This value corresponds to the longest orbital period for known redback candidates and confirmed systems in Galactic globular clusters and one of the few with a period longer than 1 day.

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