Star clusters with primordial binaries - I. Dynamical evolution of isolated models

Heggie, Douglas C.; Trenti, Michele; Hut, Piet

doi:10.1111/j.1365-2966.2006.10122.x

Cited by 88 publications

(113 citation statements)

References 38 publications

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“…Note that the results we compare with below from Heggie et al (2006) adopt the density-weighted average definition of the core radius. As shown in Figure 13, the two definitions differ minimally when the cluster is in the binaryburning phase.…”

Section: Standard Definitionsmentioning

confidence: 99%

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

Fregeau

Rasio

2007

ApJ

158

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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Section: Standard Definitionsmentioning

confidence: 99%

“…Heggie et al (2006) have shown that equation (20) Table 1). The top panel shows M b , the total mass in binaries bound to the cluster (solid line), and M, the total mass of the cluster (dashed line), as functions of time relative to their initial values.…”

Section: Comparison With Theorymentioning

confidence: 99%

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

Fregeau

Rasio

2007

ApJ

158

189

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“…To contribute significantly, a cluster must have had a sufficiently small initial relaxation time to allow the formation of an IMBH through some mild runaway process when the cluster was young, yet not have formed an IMBH with M > 350 M (since this would put IMRIs beyond the Advanced LIGO frequency range). Recent theoretical arguments by Trenti and colleagues (Heggie et al 2006;Trenti et al 2007aTrenti et al , 2007bTrenti 2006) suggest that dynamically old globulars with large core-to-half-mass radius ratios have been heated by a $1000 M IMBH, so these clusters would not contribute to the Advanced LIGO IMRI rate. Note, however, that Hurley (2007) has shown that current observations of the core-to-half-light ratios in globulars do not require 1000 M BHs in most clusters.…”

Section: Number Density Of Globulars With a Suitable Imbhmentioning

confidence: 99%

Rates and Characteristics of Intermediate Mass Ratio Inspirals Detectable by Advanced LIGO

Mandel

Brown

Gair

et al. 2008

ApJ

129

179

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Gravitational waves (GWs) from the inspiral of a neutron star ( NS) or stellar-mass black hole ( BH ) into an intermediate-mass black hole ( IMBH ) with mass M $ 50 350 M may be detectable by the planned advanced generation of ground-based GW interferometers. Such intermediate mass ratio inspirals (IMRIs) are most likely to be found in globular clusters. We analyze four possible IMRI formation mechanisms: (1) hardening of an NS-IMBH or BH-IMBH binary via three-body interactions, (2) hardening via Kozai resonance in a hierarchical triple system, (3) direct capture, and (4) inspiral of a CO from a tidally captured main-sequence star; we also discuss tidal effects when the inspiraling object is an NS. For each mechanism we predict the typical eccentricities of the resulting IMRIs. We find that IMRIs will have largely circularized by the time they enter the sensitivity band of ground-based detectors. Hardening of a binary via three-body interactions, which is likely to be the dominant mechanism for IMRI formation, yields eccentricities under 10 À4 when the GW frequency reaches 10 Hz. Even among IMRIs formed via direct captures, which can have the highest eccentricities, around 90% will circularize to eccentricities under 0.1 before the GW frequency reaches 10 Hz. We estimate the rate of IMRI coalescences in globular clusters and the sensitivity of a network of three Advanced LIGO detectors to the resulting GWs. We show that this detector network may see up to tens of IMRIs per year, although rates of one to a few per year may be more plausible. We also estimate the loss in signal-to-noise ratio that will result from using circular IMRI templates for data analysis and find that, for the eccentricities we expect, this loss is negligible.

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“…where N s and N b are the initial numbers of binaries and single stars, respectively (e.g., Kroupa 1995;Jahreiß & Wielen 2000;Heggie et al 2006). The period-generating function for the primordial binaries was given by (Kroupa 1995, Eq.…”

Section: Parameter Spacementioning

confidence: 99%

Simulations of the Hyades

Ernst

Just

Berczik

et al. 2011

A&A

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Context. Using recent observational data we present N-body simulations of the Hyades open cluster. Aims. We make an attempt to determine the initial conditions of the Hyades cluster at the time of its formation to reproduce the present-day cumulative mass profile, stellar mass and luminosity function (LF). Methods. We performed direct N-body simulations of the Hyades in an analytic Milky Way potential. They account for stellar evolution and include primordial binaries in a few models. Furthermore, we applied a Kroupa initial mass function and used extensive ensemble-averaging. Results. We find that evolved single-star King initial models with King parameters W 0 = 6−9 and initial particle numbers N 0 = 3000 provide good fits to the present-day observational cumulative mass profile within the Jacobi radius. The best-fit King model has an initial mass of 1721 M and an average mass loss rate of −2.2 M /Myr. The K-band LFs of models and observations show reasonable agreement. Mass segregation is detected in both observations and models. If 33% primordial binaries are included, the initial particle number is reduced by 5% as compared to the model without primordial binaries.Conclusions. The present-day properties of the Hyades can be reproduced well by a standard King or Plummer initial model when choosing appropriate initial conditions. The degeneracy of good-fitting models can be quite high due to the large dimension of the parameter space. More simulations with different Roche-lobe filling factors and primordial binary fractions are required to explore this degeneracy in more detail.

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Star clusters with primordial binaries - I. Dynamical evolution of isolated models

Cited by 88 publications

References 38 publications

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

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

Rates and Characteristics of Intermediate Mass Ratio Inspirals Detectable by Advanced LIGO

Simulations of the Hyades

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