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Merging supermassive black hole binaries is expected as a consequence of galaxy mergers, yet the detailed evolution path and underlying merging mechanisms of these binaries are still subject to large theoretical uncertainties. In this work,…
Using a population synthesis approach, we compute the total merger rate in the local Universe for double neutron stars, double black holes, and black hole -- neutron star binaries. These compact binaries are the prime source candidates for…
We consider the information that can be derived about massive black-hole binary populations and their formation history solely from current and possible future pulsar timing array (PTA) results. We use models of the stochastic…
Young star clusters are the most common birth-place of massive stars and are dynamically active environments. Here, we study the formation of black holes (BHs) and binary black holes (BBHs) in young star clusters, by means of 6000 N-body…
Gravitational-wave observations have just started probing the properties of black hole binary merger populations. The observation of binaries with very massive black holes and significantly asymmetric masses motivates the study of dense…
We analyze the LIGO/Virgo GWTC-2 catalog to study the primary mass distribution of the merging black holes. We perform hierarchical Bayesian analysis, and examine whether the mass distribution has a sharp cutoff for primary black hole…
In this paper we study the evolution of a primordial black hole binary (BHB) in a sample of over 1500 direct-summation $N-$body simulations of small-and intermediate-size isolated star clusters as proxies of galactic open clusters. The BHBs…
Scalar fields of masses between $10^{-21}\rm{eV}/c^2$ and $10^{-11} \rm{eV}/c^2$ can exhibit enhanced gravitational interactions with black holes, and form scalar clouds around them. Such a cloud modifies the dynamics of a coalescing…
Dense environments hosting compact binary mergers can leave an imprint on the gravitational-wave emission which, in turn, can be used to identify the characteristics of the environment. To demonstrate such scenario, we consider a simple…
The Laser Interferometer Gravitational-Wave Observatory, LIGO, found direct evidence for double black hole binaries emitting gravitational waves. Galactic nuclei are expected to harbor the densest population of stellar-mass black holes. A…
Supermassive black holes are prevalent at the centers of massive galaxies, and their masses scale with galaxy properties, increasing evidence suggesting that these trends continue to low stellar masses. Seeds are needed for supermassive…
Mainly motivated by the recent GW190521 mass gap event which we take as a benchmark point, we critically assess if binaries made of a primordial black hole and a black hole of astrophysical origin may form, merge in stellar clusters and…
The population of black holes observed via gravitational waves currently covers the local universe up to a redshift $z\lesssim 1$, for the most massive merging binaries, or $z\lesssim 0.25$ for low-mass BH binaries (BBH). Evolution of the…
Determining the astrophysical origin of binary black holes and whether merger remnants are retained in their birth environments is essential for understanding hierarchical mergers and the growth of intermediate-mass black holes. We…
We investigate the formation of intermediate mass black holes (IMBHs) through hierarchical mergers of stellar origin black holes (BHs), as well as BH mergers formed dynamically in nuclear star clusters. Using a semi-analytical approach…
The origin of the black hole (BH) binary mergers observed by LIGO-Virgo is still uncertain, as are the boundaries of the stellar BH mass function. Stellar evolution models predict a dearth of BHs both at masses $\gtrsim 50$ M$_\odot$ and…
Pair-instability should prevent the direct formation of black holes above about $50M_\odot$ creating a pair-instability mass gap. Yet gravitational-wave observations have detected black holes in this mass range. These systems can be…
The binary black hole mergers observed by LIGO-Virgo gravitational-wave detectors pose two major challenges: (i) how to produce these massive black holes from stellar processes; and (ii) how to bring them close enough to merge within the…
Recently, the LIGO-Virgo collaborations have reported the coalescence of a binary involving a black hole and a low-mass gap object (LMGO) with mass in the range $\sim2.5-5M_\odot$. Such detections, challenge our understanding of the black…
Ultralight bosons are a proposed solution to outstanding problems in cosmology and particle physics: they provide a dark-matter candidate while potentially explaining the strong charge-parity problem. If they exist, ultralight bosons can…