Binary evolution in Stellar systems

Aarseth, Sverre J.

doi:10.1007/bf00649162

Cited by 36 publications

(28 citation statements)

References 2 publications

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“…The motivation for the present investigation goes back more than 40 years. Thus an early simulation demonstrated that two massive bodies (factor of 5) gave up kinetic energy to the other members and reached the centre after a few crossing times (Aarseth 1971). Since most of the other core particles were expelled, the two dominant members invariably formed a binary.…”

Section: Introductionmentioning

confidence: 99%

Mergers and ejections of black holes in globular clusters

Aarseth¹

2012

Monthly Notices of the Royal Astronomical Society

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We report on results of fully consistent N-body simulations of globular cluster models with N = 100 000 members containing neutron stars and black holes. Using the improved `algorithmic regularization' method of Hellstrom and Mikkola for compact subsystems, the new code NBODY7 enables for the first time general relativistic coalescence to be achieved for post-Newtonian terms and realistic parameters. Following an early stage of mass segregation, a few black holes form a small dense core which usually leads to the formation of one dominant binary. The subsequent evolution by dynamical shrinkage involves the competing processes of ejection and mergers by radiation energy loss. Unless the binary is ejected, long-lived triple systems often exhibit Kozai cycles with extremely high inner eccentricity (e > 0.999) which may terminate in coalescence at a few Schwarzschild radii. A characteristic feature is that ordinary stars as well as black holes and even BH binaries are ejected with high velocities. On the basis of the models studied so far, the results suggest a limited growth of a few remaining stellar mass black holes in globular clusters.Comment: 8 pages, 9 figures, accepted MNRAS, small typo correcte

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Section: Introductionmentioning

confidence: 99%

Mergers and ejections of black holes in globular clusters

Aarseth¹

2012

Monthly Notices of the Royal Astronomical Society

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“…The core collapse leads to high stellar density region at the cluster center. Owing to the high stellar density, binaries are formed through three-body encounters (Aarseth, 1971;Heggie, 1975;Hut, 1985;Goodman & Hut, 1993). These binaries play important roles for post-collapse evolution, triggering re-expansion of the core, as well as gravothermal oscillations (Bettwieser & Sugimoto, 1983;Makino, 1996).…”

Section: Introductionmentioning

confidence: 99%

Unexpected formation modes of the first hard binary in core collapse

2012

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The conventional wisdom for the formation of the first hard binary in core collapse is that three-body interactions of single stars form many soft binaries, most of which are quickly destroyed, but eventually one of them survives. We report on direct N-body simulations to test these ideas, for the first time. We find that both assumptions are often incorrect: 1) quite a few three-body interactions produce a hard binary from scratch; 2) and in many cases there are more than three bodies directly and simultaneously involved in the production of the first binary. The main reason for the discrepancies is that the core of a star cluster, at the first deep collapse, contains typically only five or so stars. Therefore, the homogeneous background assumption, which still would be reasonable for, say, 25 stars, utterly breaks down. There have been some speculations in this direction, but we demonstrate this result here explicitly, for the first time.

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“…Aarseth 1971). The early works concentrated on the formation of binaries in star clusters with initially pure single stellar systems.…”

Section: Introductionmentioning

confidence: 99%

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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Binary evolution in Stellar systems

Cited by 36 publications

References 2 publications

Mergers and ejections of black holes in globular clusters

Mergers and ejections of black holes in globular clusters

Unexpected formation modes of the first hard binary in core collapse

Evolution of the binary population in young dense star clusters

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