Searches for Binary Stars in Globular Clusters

AbstractAstronomers have constructed models of globular clusters for over 100 years. These models mainly fall into two categories: (i) static models, such as King's model and its variants, and (ii) evolutionary models. Most attention has been given to static models, which are used to estimate mass-to-light ratios and mass segregation, and to combine data from proper motions and radial velocities. Evolutionary models have been developed for a few objects using the gaseous model, the Fokker-Planck model, Monte Carlo models and N-body models. These models have had a significant role in the search for massive black holes in globular clusters, for example.In this presentation the problems associated with these various techniques will be summarised, and then we shall describe new work with Giersz's Monte Carlo code, which has been enhanced recently to include the stellar evolution of single and binary stars. We describe in particular recent attempts to model the nearby globular cluster M4, including predictions on the spatial distribution of binary stars and their semi-major axis distribution, to illustrate the effects of about 12 Gyr of dynamical evolution. We also discuss work on an approximate way of predicting the “initial” conditions for such modelling.

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FAR-ULTRAVIOLET SURVEYS OF GLOBULAR CLUSTERS: HUNTING FOR THE PRODUCTS OF STELLAR COLLISIONS AND NEAR MISSES

Modern Physics Letters A ◽

10.1142/s0217732304015282 ◽

2004 ◽

Vol 19 (27) ◽

pp. 2013-2027 ◽

Cited By ~ 7

Author(s):

CHRISTIAN KNIGGE

Keyword(s):

Binary Stars ◽

Globular Clusters ◽

Dynamical Evolution ◽

Stellar Populations ◽

Short Review ◽

Stellar Systems ◽

Near Misses ◽

Close Encounters ◽

Stellar Collisions ◽

Far Ultraviolet

Globular clusters are gravitationally bound stellar systems containing on the order of 105 stars. Due to the high stellar densities in the cores of these clusters, close encounters and even physical collisions between stars are inevitable. These dynamical interactions can produce exotic types of single and binary stars that are extremely rare in the galactic field, but which may be important to the dynamical evolution of their host clusters. A common feature of these dynamically-formed stellar populations is that many of their members are relatively hot, and thus bright in the far-ultraviolet (FUV) waveband. In this short review, we describe how space-based FUV observations are being used to find and study these populations.

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Dynamics of primordial binary stars in multiple-population globular clusters

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315007887 ◽

2014 ◽

Vol 10 (S312) ◽

pp. 237-238

Author(s):

Jongsuk Hong ◽

Enrico Vesperini ◽

Antonio Sollima ◽

Steve McMillan ◽

Franca D'Antona ◽

...

Keyword(s):

Spatial Distribution ◽

Binding Energy ◽

Binary Stars ◽

Globular Clusters ◽

First Generation ◽

Dynamical Evolution ◽

Binary Number ◽

High Binding Energy ◽

Number Ratio ◽

Multiple Population

AbstractWe have performed a survey of N-body simulations to explore the dynamics of primordial binaries in multiple-population globular clusters. We show that, as a consequence of the initial differences between the spatial distribution of first-generation (FG) and second-generation (SG) stars, SG binaries are disrupted more efficiently than FG binaries. The effects of dynamical evolution on the surviving binaries produces a difference between the SG and the FG binary binding energy distribution with the SG population characterized by a larger fraction of high binding energy (more bound) binaries. We also explore the evolution of the radial variation of the SG-to-FG binary number ratio and find that although the global binary fraction decreases more rapidly for the SG population, the local binary fraction measured in the cluster inner regions may still be dominated by SG binaries.

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Exotic populations in globular clusters: blue stragglers as tracers of the internal dynamical evolution of stellar systems

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315007772 ◽

2014 ◽

Vol 10 (S312) ◽

pp. 171-180

Author(s):

Francesco R. Ferraro

Keyword(s):

Radial Distribution ◽

Globular Clusters ◽

Stellar Population ◽

Dynamical Evolution ◽

Stellar Systems ◽

Internal Dynamics ◽

Blue Stragglers ◽

Blue Straggler ◽

Specific Frequency ◽

Definition Of

AbstractIn this paper I present an overview of the main observational properties of a special class of exotic objects (the so-called Blue Straggler Stars, BSSs) in Galactic Globular Clusters (GCs). The BSS specific frequency and their radial distribution are discussed in the framework of using this stellar population as probe of GC internal dynamics. In particular, the shape of the BSS radial distribution has been found to be a powerful tracer of the dynamical evolution of stellar systems, thus allowing the definition of an empirical “clock”able to measure the dynamical age of stellar aggregates from pure observational properties.

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The Discovery of a Spectroscopic Binary in M 3

International Astronomical Union Colloquium ◽

10.1017/s0252921100098882 ◽

1984 ◽

Vol 88 ◽

pp. 269-273

Author(s):

David W. Latham ◽

Martha L. Hazen-Liller ◽

Carleton P. Pryor

Keyword(s):

Globular Cluster ◽

Binary Stars ◽

Globular Clusters ◽

Stellar Population ◽

Radial Velocities ◽

Velocity Variation ◽

Spectroscopic Binary ◽

Strong Candidate

AbstractBinary stars appear to be a pervasive feature of the sidereal universe. In every stellar population or habitat that has been investigated, except globular clusters, from 10 to 40 percent of the objects observed prove to have variable radial velocities that suggest they are spectroscopie binaries. To extend the search for spectroscopie binaries in the globular cluster M3, we have obtained more than 300 new radial velocities for the 111 giants previously observed by Gunn and Griffin (1979). For one of the stars, von Zeipel 164, four observations spanning ten years show a velocity variation with an amplitude of at least 18 km s−1 and a period of perhaps a few years. We believe this is a strong candidate for the first spectroscopie binary to be found in a globular cluster.

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An empirical clock to measure the dynamical age of star clusters

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319008202 ◽

2019 ◽

Vol 14 (S351) ◽

pp. 377-383

Author(s):

Francesco R. Ferraro

Keyword(s):

Radial Distribution ◽

Special Class ◽

Globular Clusters ◽

Stellar Population ◽

Star Clusters ◽

Dynamical Evolution ◽

Stellar Systems ◽

Central Segregation ◽

Blue Straggler ◽

Definition Of

AbstractThe observational properties of a special class of stars (the so-called Blue Straggler stars - BSSs) in Globular Clusters are discussed in the framework of using this stellar population as probe of the dynamical processes occurring in high-density stellar systems. In particular, the shape of the BSS radial distribution and their level of central segregation have been found to be powerful tracers of the level of the dynamical evolution of the hosting cluster, thus allowing the definition of an empirical chronometer able to measure the dynamical age of star clusters.

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The Hubble Space Telescope UV Legacy Survey of Galactic globular clusters – XXI. Binaries among multiple stellar populations

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3629 ◽

2019 ◽

Vol 492 (4) ◽

pp. 5457-5469

Author(s):

A P Milone ◽

E Vesperini ◽

A F Marino ◽

J Hong ◽

R van der Marel ◽

...

Keyword(s):

Numerical Simulations ◽

Binary Stars ◽

Globular Clusters ◽

First Generation ◽

Hubble Space Telescope ◽

Dynamical Evolution ◽

Stellar Populations ◽

Multiple Populations ◽

Space Telescope ◽

Significant Difference

Abstract A number of scenarios for the formation of multiple populations in globular clusters (GCs) predict that second generation (2G) stars form in a compact and dense subsystem embedded in a more extended first-generation (1G) system. If these scenarios are accurate, a consequence of the denser 2G formation environment is that 2G binaries should be more significantly affected by stellar interactions and disrupted at a larger rate than 1G binaries. The fractions and properties of binary stars can thus provide a dynamical fingerprint of the formation epoch of multiple-population GCs and their subsequent dynamical evolution. We investigate the connection between binaries and multiple populations in five GCs, NGC 288, NGC 6121 (M 4), NGC 6352, NGC 6362, and NGC 6838 (M 71). To do this, we introduce a new method based on the comparison of Hubble Space Telescope observations of binaries in the F275W, F336W, F438W, F606W, and F814W filters with a large number of simulated binaries. In the inner regions probed by our data, we do not find large differences between the local 1G and the 2G binary incidences in four of the studied clusters, the only exception being M 4 where the 1G binary incidence is about three times larger than the 2G incidence. The results found are in general agreement with the results of simulations predicting significant differences in the global 1G and 2G incidences and in the local values in the clusters’ outer regions but similar incidences in the inner regions. The significant difference found in M 4 is consistent with simulations with a larger fraction of wider binaries. Our analysis also provides the first evidence of mixed (1G–2G) binaries, a population predicted by numerical simulations to form in a cluster’s inner regions as a result of stellar encounters during which one component of a binary is replaced by a star of a different population.

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Dynamics of Multiple Stellar Populations in Globular Clusters

Proceedings of the International Astronomical Union ◽

10.1017/s174392131400564x ◽

2012 ◽

Vol 10 (H16) ◽

pp. 251-252

Author(s):

Enrico Vesperini ◽

Steve McMillan ◽

Franca D'Antona ◽

Annibale D'Ercole

Keyword(s):

Structural Properties ◽

Binary Stars ◽

Globular Clusters ◽

Galactic Halo ◽

Dynamical Evolution ◽

Stellar Populations ◽

Multiple Population

AbstractThe results of numerous spectroscopic and photometric studies have revealed the presence of multiple stellar populations in many globular clusters. In this paper we summarize the results of our recent studies on the dynamical evolution of multiple-population clusters, the implications of the structural properties of multiple-population clusters for the evolution of binary stars, and the possible contribution of globular clusters to the assembly of the Galactic halo.

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MOCCA survey database I: Preliminary mock Extra Galactic Globular Cluster observations

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319007075 ◽

2019 ◽

Vol 14 (S351) ◽

pp. 122-125

Author(s):

Agostino Leveque ◽

Mirosław Giersz

Keyword(s):

Spatial Distribution ◽

Globular Cluster ◽

Globular Clusters ◽

Surface Brightness ◽

Stellar Population ◽

Dynamical Evolution ◽

The Other ◽

Population Synthesis ◽

Stellar Population Synthesis ◽

Preliminary Study

AbstractThe photometric properties that we could observe for Extra-Galactic Globular Clusters (EGGCs) are the integrated light of the system and for nearby EGGCs it also is possible to measure both half-light radii and the color spatial distribution, e.g. for areas smaller and larger than the half-light radius. No information about the internal dynamical state of the system could be directly obtained from observations. On the other hand, simulations of Globular Clusters (GCs) can provide detailed information about the dynamical evolution of the system.We present a preliminary study of EGGCs’ photometric properties for different dynamical evolutionary stages. We apply this study to 12Gyr old GCs simulated as part of the MOCCA Survey Database. We determine the magnitudes in different bands from their projected snapshots using the Flexible Stellar Population Synthesis (FSPS) code and we measure the half-light radii from the surface brightness.

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Dynamical evolution of multiple-population globular clusters

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab223 ◽

2021 ◽

Vol 502 (3) ◽

pp. 4290-4304

Author(s):

Enrico Vesperini ◽

Jongsuk Hong ◽

Mirek Giersz ◽

Arkadiusz Hypki

Keyword(s):

Structural Properties ◽

Globular Clusters ◽

First Generation ◽

Radial Profile ◽

Dynamical Evolution ◽

Evolutionary Phase ◽

Dynamical Parameters ◽

Energy Equipartition

ABSTRACT We have carried out a set of Monte Carlo simulations to study a number of fundamental aspects of the dynamical evolution of multiple stellar populations in globular clusters with different initial masses, fractions of second generation (2G) stars, and structural properties. Our simulations explore and elucidate: (1) the role of early and long-term dynamical processes and stellar escape in the evolution of the fraction of 2G stars and the link between the evolution of the fraction of 2G stars and various dynamical parameters; (2) the link between the fraction of 2G stars inside the cluster and in the population of escaping stars during a cluster’s dynamical evolution; (3) the dynamics of the spatial mixing of the first-generation (1G) and 2G stars and the details of the structural properties of the two populations as they evolve toward mixing; (4) the implications of the initial differences between the spatial distribution of 1G and 2G stars for the evolution of the anisotropy in the velocity distribution and the expected radial profile of the 1G and 2G anisotropy for clusters at different stages of their dynamical history; and (5) the variation of the degree of energy equipartition of the 1G and the 2G populations as a function of the distance from the cluster’s centre and the cluster’s evolutionary phase.

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