Related papers: Resonant Dynamical Friction Around a Super-Massive…
The discovery of quasars at increasingly large cosmological redshifts may favor "direct collapse" as the most promising evolutionary route to the formation of supermassive black holes. In this scenario, supermassive black holes form when…
One of the greatest issues in modelling black hole fuelling is our lack of understanding of the processes by which gas loses angular momentum and falls from galactic scales down to the nuclear region where an accretion disc forms,…
We study the long-term orbital evolution of stars around a merging massive or supermassive black-hole (BH) binary, taking into account the general relativistic effect induced by the BH spin. When the BH spin is significant compared to and…
Quasi-periodic eruptions (QPEs) are recently discovered transients of unknown nature occurring near supermassive black holes, which feature bright X-ray bursts separated by hours to days. A promising model for QPEs is the star-disc…
Stellar-mass binaries evolving in the vicinity of supermassive black holes (SMBHs) may be common in the universe, either in active galactic nuclei or in other astrophysical environments. Here, we study in detail the resonant excitation of…
Accretion in the nuclei of active galaxies may occur chaotically. This can produce accretion discs which are counter-rotating or strongly misaligned with respect to the spin of the central supermassive black hole (SMBH), or the axis of a…
Dynamical friction is often modeled with reasonable accuracy by the widely used Chandrasekhar formula. However, in some circumstances, Chandrasekhar's local and uniform approximations can break down severely. An astrophysically important…
An inspiralling object of mass $\mu$ around a Kerr black hole of mass $M (\gg \mu)$ experiences a continuous transition near the innermost stable circular orbit from adiabatic inspiral to plunge into the horizon as gravitational radiation…
We study a new channel for binary system formation involving stars and stellar-mass primordial black holes (PBHs) embedded in dark matter (DM) minihalos. In this scenario, binaries form when a star passes through the DM minihalo surrounding…
The association of an electromagnetic signal with the merger of a pair of supermassive black holes would have many important implications. For example, it would provide new information about gas and magnetic field interactions in dynamical…
It is now well-established that a dark, compact object (DCO), very likely a massive black hole (MBH) of around four million solar masses is lurking at the centre of the Milky Way. While a consensus is emerging about the origin and growth of…
In the vicinity of a massive black hole, stars move on precessing Keplerian orbits. The mutual stochastic gravitational torques between the stellar orbits drive a rapid reorientation of their orbital planes, through a process called vector…
A circumbinary disc around a pair of merging stellar-mass black holes may be shocked and heated during the recoil of the merged hole, causing a near-simultaneous electromagnetic counterpart to the gravitational wave event. The shocks occur…
We study the formation of a supermassive black hole (SMBH) binary and the shrinking of the separation of the two holes to sub-pc scales starting from a realistic major merger between two gas-rich spiral galaxies with mass comparable to our…
Observations of accreting systems often show significant variability (10-20 percent of accretion luminosity) on timescales much longer than expected for the disc regions releasing most of the luminosity. We propose an explicit physical…
Recent analyses have shown that close encounters between stars and stellar black holes occur frequently in dense star clusters. Depending upon the distance at closest approach, these interactions can lead to dissipating encounters such as…
Dynamical friction is an important phenomena in stellar dynamics resulting in the slowing down of a test particle upon many two-body scatters with background particles. Chandrasekhar's original formulation, developed for idealized infinite…
We show that main-sequence stars in dense stellar cusps around massive black holes are likely to rotate at a significant fraction of the centrifugal breakup velocity due to spin-up by hyperbolic tidal encounters. We use realistic stellar…
After the Tidal Disruption Event (TDE) of a star around a SuperMassive Black Hole (SMBH), the bound stellar debris rapidly forms an accretion disk. If the accretion disk is not aligned with the spinning SMBH's equatorial plane, the disk…
We argue that supermassive black hole growth in AGN occurs via sequences of randomly--oriented accretion discs with angular momentum limited by self--gravity. These stably co-- or counter--align with the black hole spin with almost equal…