The evolution of binary fractions in globular clusters

Іванова, Наталя; Belczyński, K.; Fregeau, John M.; Rasio, Frederic A.

doi:10.1111/j.1365-2966.2005.08804.x

Cited by 188 publications

(262 citation statements)

References 62 publications

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“…Theoretical studies of the evolution of binary populations are unaffected by from this shortcoming but usually also use this simple observable for reasons of comparison with observational data (see for example Kroupa 1995a; Kroupa & Bouvier 2003;Ivanova et al 2005;Hurley et al 2007;Sollima 2008). If we also do this here, we obtain the result described by Fig.…”

Section: Resultsmentioning

confidence: 99%

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Evolution of the binary population in young dense star clusters

Kaczmarek

Olczak

Pfalzner

2011

A&A

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Context. Field stars are not always single stars, but can often be found in bound double systems. Since binary frequencies in the birth places of stars, young embedded clusters, are sometimes even higher than on average the question arises of how binary stars form in young dense star clusters and how their properties evolve to those observed in the field population. Aims. We assess, the influence of stellar dynamical interactions on the primordial binary population in young dense cluster environments. Methods. We perform numerical N-body simulations of the Orion nebula cluster like star cluster models including primordial binary populations using the simulation code nbody6 ++ . Results. We find two remarkable results that have yet not been reported: The first is that the evolution of the binary frequency in young dense star clusters is independent predictably of its initial value. The time evolution of the normalized number of binary systems has a fundamental shape. The second main result is that the mass of the primary star is of vital importance to the evolution of the binary. The more massive a primary star, the lower the probability that the binary is destroyed by gravitational interactions. This results in a higher binary frequency for stars more massive than 2 M compared to the binary frequency of lower mass stars. The observed increase in the binary frequency with primary mass is therefore most likely not due to differences in the formation process but can be entirely explained as a dynamical effect. Conclusions. Our results allow us to draw conclusions about the past and the future number of binary systems in young dense star clusters and demonstrate that the present field stellar population has been influenced significantly by its natal environments.

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Section: Resultsmentioning

confidence: 99%

“…A flat binary period distribution has not only been observed in Sco OB II but also in other regions (e.g. Connelley et al 2008;Reipurth et al 2007) and has been used in several theoretical studies involving the evolution of primordial binary frequencies (Heggie & Aarseth 1992;Ivanova et al 2005;Hurley et al 2007). …”

Section: Methods and Cluster Setupmentioning

confidence: 99%

Evolution of the binary population in young dense star clusters

Kaczmarek

Olczak

Pfalzner

2011

A&A

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“…An initial binary fraction of a few percent is enough to postpone deep core collapse for many initial relaxation times (see Fregeau et al [2003] for discussion and references). In addition to playing a large part in the global evolution of a star cluster, dynamical interactions of binaries also strongly affect the formation and evolution of stellar and binary exotica, which include low-mass X-ray binaries, recycled pulsars, cataclysmic variables, and blue stragglers ( Hut et al 1991;Sigurdsson & Phinney 1995;Davies & Hansen 1998;Rasio et al 2000;Ivanova et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo Simulations of Globular Cluster Evolution. IV. Direct Integration of Strong Interactions

Fregeau

Rasio

2007

ApJ

159

189

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We study the dynamical evolution of globular clusters containing populations of primordial binaries, using our newly updated Monte Carlo cluster evolution code with the inclusion of direct integration of binary scattering interactions. We describe the modifications we have made to the code, as well as improvements we have made to the core Monte Carlo method. We present several test calculations to verify the validity of the new code and perform many comparisons with previous analytical and numerical work in the literature. We simulate the evolution of a large grid of models, with a wide range of initial cluster profiles and with binary fractions ranging from 0 to 1, and compare with observations of Galactic globular clusters. We find that our code yields very good agreement with direct N-body simulations of clusters with primordial binaries, but yields some results that differ significantly from other approximate methods. Notably, the direct integration of binary interactions reduces their energy generation rate relative to the simple recipes used in Paper III and yields smaller core radii. Our results for the structural parameters of clusters during the binary-burning phase are now in the tail of the range of parameters for observed clusters, implying that either clusters are born significantly more or less centrally concentrated than has been previously considered or there are additional physical processes beyond two-body relaxation and binary interactions that affect the structural characteristics of clusters.

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“…The binary evolution can also lead to their disruption (e.g., supernova explosions, star mergers, etc.). Furthermore, Ivanova et al (2005) have suggested that, to explain the currently observed low fraction of binary systems in cluster cores, the initial ratio of stars in binaries to all stars in GCs should be very high (even close to 100%). This means that the population of binary systems is much higher when a GC is formed, and that binaries may play an important role in the evolution of GCs.…”

Section: Discussionmentioning

confidence: 99%

Effects of tidally enhanced stellar wind on the horizontal branch morphology of globular clusters

Lei

Chen

Zhang

et al. 2013

A&A

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Context. Metallicity is the first parameter to influence the horizontal branch (HB) morphology of globular clusters (GCs). It has been found, however, that some other parameters may also play an important role in affecting the morphology. While the nature of these important parameters remains unclear, they are believed to be likely correlated with wind mass-loss of red giants, since this mass loss determines their subsequent locations on the HB. Unfortunately, the mass loss during the red giant stages of the stellar evolution is poorly understood at present. Aims. The stellar winds of red giants may be tidally enhanced by companion stars if they are in binary systems. We investigate the evolutionary consequences of red giants in binaries by including tidally enhanced stellar winds, and examine the effects on the HB morphology of GCs. Methods. We used Eggleton's stellar evolution code to study the binary evolution. The tidally enhanced stellar-wind model of Tout & Eggleton is incorporated into this code, where the tidal enhancement parameter, B w , has various values (e.g., 10 000 and 500) to examine the dependency of the final results on this parameter. A Monte Carlo simulation was performed to generate a group of binary systems. The position of each primary star on the HB in the Hertzsprung-Russell diagram in this sample is obtained through interpolations among the constructed HB evolutionary tracks. Finally, a synthetic HB in the color-magnitude diagram is obtained by transforming the effective temperature and luminosity of each primary star on the HB into B − V colors and absolute magnitude. Results. We find that red, blue, and extreme horizontal branch stars are all produced under the effects of tidally enhanced stellar wind without any additional assumptions on the mass-loss dispersion. Furthermore, the horizontal branch morphology is found to be insensitive to the tidal enhancement parameter, B w . We compare our theoretical results with the observed horizontal branch morphology of globular cluster NGC 2808, and find that the basic morphology of the horizontal branch can be well reproduced. The number of blue horizontal branch stars in our calculations, however, is lower than that of NGC 2808.

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The evolution of binary fractions in globular clusters

Cited by 188 publications

References 62 publications

Evolution of the binary population in young dense star clusters

Evolution of the binary population in young dense star clusters

Monte Carlo Simulations of Globular Cluster Evolution. IV. Direct Integration of Strong Interactions

Effects of tidally enhanced stellar wind on the horizontal branch morphology of globular clusters

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