7476469
Observing IMBH-IMBH Binary Coalescences via Gravitational Radiation
Recent numerical simulations have suggested the possibility of forming double intermediate-mass black holes (IMBHs) via the collisional runaway scenario in young dense star clusters. The two IMBHs that formed would exchange into a common binary shortly after their birth and quickly inspiral and merge. Since space-borne gravitational wave (GW) observatories such as LISA will be able to see the late phases of their inspiral out to several gigaparsecs, and LIGO will be able to see the merger and ringdown out to similar distances, they represent potentially significant GW sources. In this Letter we estimate the rate at which LISA and LIGO will see their inspiral and merger in young star clusters, and we discuss the information that can be extracted from the observations. We find that LISA will likely see tens of IMBH-IMBH inspirals per year, while advanced LIGO could see ∼10 merger and ringdown events per year, with both rates strongly dependent on the distribution of cluster masses and densities. Subject headings: black hole physics — gravitational waves — stellar dynamics
117981136
Run-away formation of intermediate-mass black holes in dense star clusters
We consider spherical stellar clusters with a broad mass function and a relaxation time short enough so that the segregation of massive stars toward the centre occurs before they have time to evolve off the main sequence. The relaxational and collisional dynamics of model clusters is followed with a high-resolution Monte Carlo code. Stellar collisions are treated in a realistic way, through the use of a outcome of a very large set of SPH simulations. We find that, even in proto-galactic nuclei models with high velocity dispersions, run-away growth of a very massive star (VMS, M>100 M_sun) occurs in all cases when the core collapse time is shorter than the MS life time of massive stars, i.e. 3 Myrs. The VMS is a likely progenitor for an intermediate-mass or massive black hole (IMBH/MBH).
16368134
The Final Fate of Coalescing Binary Neutron Stars: Collapse to a Black Hole?
Coalescing compact binaries with neutron star (NS) or black hole (BH) components are important sources of gravitational waves for the laser-interferometer detectors currently under construction, and may also be sources of gamma-ray bursts at cosmological distances. This paper focuses on the final hydrodynamic coalescence and merger of NS--NS binaries, and addresses the question of whether black hole formation is the inevitable final fate of these systems.
16148009
Could Black Hole X-Ray Binaries Be Detected in Globular Clusters?
We consider the implications of the presence of an ∼1 stellar-mass black hole (BH) at the center of a dense globular cluster. We show that BH X-ray binaries formed through exchange interactions are likely to have extremely low duty cycles (under about 10 3 ), consistent with the absence of BH X-ray transients in Galactic globular clusters. In contrast, we find that BH X-ray binaries formed through tidal capture would be persistent, bright Xray sources. Given the absence of any such source and the very high interaction rates, we conclude that tidal capture of a main-sequence star by a BH most likely leads to the complete disruption of the star. Subject headings: accretion, accretion disks — binaries: close — black hole physics — globular clusters: general — stellar dynamics
117759975
Hydrodynamics of binary coalescence
11631658
Hydrodynamic Instabilities in Close Binary Systems
Equilibrium fluid configurations for close binary systems can become {\em globally unstable\/}. Instabilities arise from the strong tidal interaction between the two components, which tends to make the effective two-body potential governing the orbital motion steeper than $1/r$. As a result, a circular orbit can become unstable to small radial perturbations. The instability can be either secular or dynamical. In both cases it leads to the coalescence and merging of the two components on a timescale generally much shorter than the lifetime of a stable system. Binary coalescence is relevant to a wide variety of astrophysical problems including the formation of blue stragglers, Type~Ia supernovae, the evolution of massive X-ray binaries, and the detection of gravitational waves.
118424765
Finding Local Low‐mass Supermassive Black Holes
The low‐mass end of the supermassive black hole mass function is unknown and difficult to determine. Here we discuss our successful program to find active nuclei of late type “normal” galaxies using X‐ray detections and multiwavelength identifications. We conclude that most of the Chandra detected nuclear X‐ray sources are AGNs. We then outline methods of black hole mass determination when broad emission lines are unobservable.