Primordial black holes in globular clusters

Sigurd̵sson, Steinn; Hernquist, Lars

doi:10.1038/364423a0

Cited by 400 publications

(420 citation statements)

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“…We note that 20% of these FBs produce a [NS, CO] binary with orbital separation such that the companion star fills its Roche lobe. This hints in favor of a '' collisionally induced '' recycling process, as suggested by Sigurdsson (2003). (Note that recycling lasts for a time less or comparable to the lifetime of the binary pulsar in the cluster halo according to dynamical friction, making this picture consistent.)…”

Section: Prerecycling Binary-binary Encountersmentioning

confidence: 57%

“…The density of neutron stars is largely unknown given the uncertainties in their retention fraction at birth, but its value is expected to be larger than the density n of stars (Sigurdsson & Hernquist 1993). The value of f is even more uncertain.…”

Section: The Statistics Of the Encountersmentioning

confidence: 99%

“…This is a necessary condition since the characteristic timescale for dynamical friction DF to drive [PSR A, CO] from the current position to the core has been estimated as $1 Gyr (see CPG ;Sigurdsson 2003). This timescale imposes a lifetime for the black hole binary comparable to the age of the cluster itself, unless the binary formed recently.…”

Section: The Binary Pulsarmentioning

confidence: 99%

“…The black holes (relics of the most massive stars) tend to pair with other black holes in binaries as soon as they segregate in the cluster core by dynamical friction (Kulkarni et al 1993). Some binaries may rapidly merge emitting gravitational waves (GWs; Benacquista 1999;Miller 2002), creating a more massive black hole (Miller & Hamilton 2002), but most/many leave the cluster since close (three-or four-body) dynamical encounters among the black holes eject them, singly or in binaries, because of recoil (Sigurdsson & Hernquist 1993;Kulkarni et al McMillan 1993). Current N-body simulations (Portegies Zwart & McMillan 2000) expect no black hole or one black hole binary to remain in the cluster.…”

Section: Introductionmentioning

confidence: 99%

“…Black hole binaries are expected to form in rich star clusters, but along the course of evolution they are expected to exit their parent cluster (Kulkarni, Hut, & McMillan 1993;Sigurdsson & Hernquist 1993). The black holes (relics of the most massive stars) tend to pair with other black holes in binaries as soon as they segregate in the cluster core by dynamical friction (Kulkarni et al 1993).…”

Section: Introductionmentioning

confidence: 99%

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Probing the Presence of a Single or Binary Black Hole in the Globular Cluster NGC 6752 with Pulsar Dynamics

Colpi

Mapelli

Possenti

2003

ApJ

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The five millisecond pulsars that inhabit NGC 6752 display locations or accelerations that are quite unusual compared to all other known pulsars in globular clusters. In particular, PSR A, a binary pulsar, lives in the cluster halo, while PSR B and PSR E, located in the core, show remarkably high negative spin derivatives. This suggests that some uncommon dynamical process is at play in the cluster core, which we attribute to the presence of a massive perturber. Here we investigate whether a single intermediate-mass black hole, lying on the extrapolation of the mass M BH versus relation observed in galaxy spheroids, or a less massive binary black hole could play the requested role. To this purpose we simulated binary-binary encounters involving PSR A, its companion star, and the black hole(s). A stellar-mass binary black hole of (50 M ; 10 M ) can impart the right thrust to propel PSR A into the halo during a flyby. The flyby is gentle and does not alter the internal properties of the binary pulsar. An intermediate-mass binary black hole of (200 M ; 10 M ) tends to impart a recoil speed larger than the escape speed: it can release PSR A on the right orbit if its separation is wide. A single intermediate-mass black hole of mass M BH e500 M may have ejected PSR A at the periphery of NGC 6752 in a close dynamical encounter involving the binary pulsar, the black hole, and a star belonging to its cusp. The encounter gives correct speeds but alters significantly the eccentricity of the impinging binary, so that it must occur before the neutron star of PSR A is recycled via accretion torque. The influence of an intermediate-mass binary black hole on the acceleration of the two core pulsars is studied, and the ejection of stars by the binary is briefly explored. In inspecting our close four-body encounters, we have found that a single or binary black hole may attract on a long-term stable orbit a millisecond pulsar. Timing measurements on the captured '' satellite '' pulsar, either a member of a hierarchical triple or a member of the cusp, could unambiguously unveil the presence of a black hole(s) in the core of a globular cluster.

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Section: Prerecycling Binary-binary Encountersmentioning

confidence: 57%

Section: The Statistics Of the Encountersmentioning

confidence: 99%

Section: The Binary Pulsarmentioning

confidence: 99%