Related papers: Gravitational-wave background from compact objects…
It is accepted that quasars are powered by supermassive black holes (SMBH) with masses in the range 10^6 - 10^9 solar masses in their cores. Occasionally, compact stars can plunge into SMBH. In addition, there may be a number of such…
We derive estimates for the characteristics of gravitational radiation from stellar collapse, using recent models of the core-collapse of Chandrasekhar mass white dwarfs (accretion induced collapse), core-collapse supernovae and collapsars,…
The inspiral of a ``small'' ($\mu \sim 1-100 M_\odot$) compact body into a ``large'' ($M \sim 10^{5-7} M_\odot$) black hole is a key source of gravitational radiation for the space-based gravitational-wave observatory LISA. The waves from…
We discuss the stochastic background of gravitational waves from ultra compact neutron star-white dwarf (NS-WD) binaries at cosmological distances. Under the assumption that accreting neutron stars and donor white dwarf stars form most of…
We constrain the number density and evolution of Compton-thick Active Galactic Nuclei (AGN). In the local Universe we use the wide area surveys from the Swift and INTEGRAL satellites, while for high redshifts we explore candidate selections…
Gravitational waves from inspiraling sub-solar mass compact objects would provide almost definitive evidence for the existence of primordial black holes. In this chapter, we explain why these exotic objects are interesting candidates for…
The accretion disks that fuel active galactic nuclei (AGN) may house numerous stars and compact objects, formed in situ or captured from nearby star clusters. Embedded neutron stars and black holes may form binaries and eventually merge,…
Accretion disks around compact objects are expected to enter an unstable phase at high luminosity. One instability may occur when the radiation pressure generated by accretion modifies the disk viscosity, resulting in the cyclic depletion…
The detection of the gravitational waves emitted in the capture process of a compact object by a massive black hole is known as an extreme-mass ratio inspiral (EMRI) and represents a unique probe of gravity in the strong regime and is one…
We perform 3D radiation hydrodynamic local shearing box simulations to study the outcome of gravitational instability (GI) in optically thick Active Galactic Nuclei (AGN) accretion disks. GI develops when the Toomre parameter QT \leq 1, and…
Gravitational instability in the outskirts of Active Galactic Nuclei (AGN) disks lead to disk fragmentation and formation of super-massive (several 10^2Msun) stars with potentially long lifetimes. Alternatively, stars can be captured…
A major amendment in recent models of hierarchical galaxy formation is the inclusion of so-called AGN feedback. The energy input from an active central massive black hole is invoked to suppress star formation in early-type galaxies at later…
The standard alpha-disc model predicts an anti-correlation between the density of the inner accretion disc and the black hole mass times square of the accretion rate, as seen in higher mass ($M_{\rm BH}>10^{6} M_{\odot}$) active galactic…
The X-ray Background (XRB) probably originates from the integrated X-ray emission of active galactic nuclei (AGN). Modelling of its flat spectrum implies considerable absorption in most AGN. Compton down-scattering means that sources in…
If binary intermediate-mass black holes (IMBHs; with masses between 100 and $10^4 \Msun$) form in dense stellar clusters, their inspiral will be detectable with the planned Laser Interferometer Space Antenna (LISA) out to several Gpc. Here…
One of the most exciting potential sources of gravitational waves for low-frequency, space-based gravitational wave (GW) detectors such as the proposed Laser Interferometer Space Antenna (LISA) is the inspiral of compact objects into…
Stars on eccentric orbits around a massive black hole (MBH) emit bursts of gravitational waves (GWs) at periapse. Such events may be directly resolvable in the Galactic centre. However, if the star does not spiral in, the emitted GWs are…
Context: Variations in the mass accretion rate appear to be responsible for the rapid transitions in spectral type that are observed in increasingly more active galactic nuclei (AGNs). These objects are now labeled "changing-look" AGNs and…
Dynamics of stellar mass black holes (sBHs) embedded in active galactic nuclei (AGNs) could produce highly eccentric orbits near the central supermassive black hole, leading to repeated close encounters that emit gravitational waves in the…
There is a lot of current interest in sources of gravitational waves and active ongoing projects to detect such radiation, such as the LIGO project. These are long wavelength, low frequency gravitational waves. LISA would be sensitive to…