Related papers: Black holes formed by direct collapse: observation…
The possible formation mechanisms of massive close binary black holes (BHs) that can merge in the Hubble time to produce powerful gravitational wave bursts detected during advanced LIGO O1 and O2 science runs include the evolution from…
The recent detections of the binary black hole mergers GW150914 and GW151226 have inaugurated the field of gravitational-wave astronomy. For the two main formation channels that have been proposed for these sources, isolated binary…
Binary black holes may form both through isolated binary evolution and through dynamical interactions in dense stellar environments. The formation channel leaves an imprint on the alignment between the black hole spins and the orbital…
The first massive astrophysical black holes likely formed at high redshifts (z>10) at the centers of low mass (~10^6 Msun) dark matter concentrations. These black holes grow by mergers and gas accretion, evolve into the population of bright…
The gravitational collapse of a spherically symmetric star, made of a dust fluid, $\rho_{DM}$, in a background of dark energy, $p = w\rho,\; (w < -1/3)$, is studied. It is found that when only dark energy is present, black holes are {\em…
Now that LIGO has revealed the existence of a large number of binary black holes, identifying their origin becomes an important challenge. They might originate in more isolated regions of the galaxy or alternatively they might reside in…
We explore the properties of dense star clusters that are likely to be the nurseries of stellar black holes pairing in close binaries. We combine a cosmological model of globular cluster formation with analytic prescriptions for the…
Stellar models indicate that the core compactness of a star, which is a common proxy for its explodability in a supernova, does not increase monotonically with the star's mass. Rather, the core compactness dips sharply over a range of…
If supermassive black holes (BHs) are generically present in galaxy centers, and if galaxies are built up through hierarchical merging, BH binaries are at least temporary features of most galactic bulges. Observations suggest, however, that…
Interest to astrophysical evidence for primordial black holes (PBHs) formed in the early Universe from initial cosmological perturbations has increased after the discovery of coalescing binary black holes with masses more than dozen solar…
There is compelling evidence that supermassive black holes exist. Yet the origin of these objects, or their seeds, is still unknown. We discuss several plausible scenarios for forming the seeds of supermassive black holes. These include the…
We analyze the mass distribution of stellar black holes derived from the light and radial velocity curves of optical stars in close binary systems using dynamical methods. The systematic errors inherent in this approach are discussed. These…
Understanding the formation of earliest supermassive black holes is a question of prime astrophysical interest. In this chapter, we focus on the formation of massive black holes via gas dynamical processes. The necessary requirement for…
We investigate black hole-star binaries formed in $N$-body simulations of massive, dense star clusters. We simulate 32 clusters with varying initial masses ($10^{4}~\rm M_{\odot}$ to $10^{6}~\rm M_{\odot}$), densities ($1200~\rm…
Mass distribution of black holes identified through X-ray emission suggests a paucity of black holes in the mass range of 3 to 5 solar masses. Modified theories have been devised to explain this mass gap, and it is suggested that natal…
In massive binary-star systems, supernova explosions can significantly alter the orbit during the formation of compact objects. Some compact objects are predicted to form via direct collapse, a scenario with negligible mass loss and no…
Observations of gravitational waves and their electromagnetic counterparts may soon uncover the existence of coalescing compact binary systems formed by a stellar-mass black hole and a neutron star. These mergers result in a remnant black…
We study the evolution of a massive black hole pair in a rotationally supported nuclear disc. The distributions of stars and gas mimic the nuclear region of a gas-rich galaxy merger remnant. Using high-resolution SPH simulations, we follow…
We develop the general formalism for joining, splitting and interconnection of closed and open strings. As an application, we study examples of fundamental cosmic string collisions leading to gravitational collapse. We find that the…
Relativistic jets powered by stellar mass black holes in X-ray binaries appear to come in two types: steady outflows associated with hard X-ray states and large scale discrete ejections associated with transient outbursts. We show that the…