Related papers: Gravitational-wave background from compact objects…
The nature of black holes is one of most exciting issues in gravitational physics. If there is an exotic compact object as the compact as a black hole but without a horizon, gravitational wave echoes may be produced after the merger. In…
Gravitational waveforms and production could be considerably affected by gravitomagnetic corrections considered in relativistic theory of orbits. Beside the standard periastron effect of General Relativity, new nutation effects come out…
Previously it was shown that gravitation theory allows the existance of supermassive stable compact configurations of the degenerated electronic gas (L.V.Verozub, Astr. Nacr. 317 (1996) 107) without events horizon. In the present paper the…
Keplerian accretion discs around massive black holes (MBHs) are gravitationally unstable beyond a few hundredths of parsec and should collapse to form stars. Indeed an accretion/star formation episode took place a few millions years ago in…
The Laser Interferometer Space Antenna (LISA) is a planned space-based observatory designed to detect gravitational waves (GWs) within the millihertz frequency range. LISA is anticipated to observe the inspiral of compact objects into black…
We estimate the rate of inspiral for a population of stellar mass BHs in the star cluster around the super massive black hole at the center of Milky Way mass galaxies. Our approach is based on an orbit averaged Fokker Planck approach. This…
Accretion disc theory predicts that an AGN disc becomes self-gravitating and breaks up into stars at an outer radius $R_{\rm sg}$ ~ 12 light-days, with effectively no free parameter. We present evidence that the longer observed AGN light…
We have incorporated the description of the X-ray properties of Active Galactic Nuclei (AGNs) into a semi-analytic model of galaxy formation, adopting physically motivated scaling laws for accretion triggered by galaxy encounters. Our model…
We study the composition of the faint radio population selected from the VLA-COSMOS 3GHz Large Project, a radio continuum survey performed at 10 cm wavelength. The survey covers the full 2 square degree COSMOS field with mean $rms\sim2.3$…
Sun-like stars can transmute into comparable mass black holes by steadily accumulating heavy non-annihilating dark matter particles over the course of their lives. If such stars form in binary systems, they could give rise to…
The inner regions of active galaxies host the most extreme and energetic phenomena in the universe including, relativistic jets, supermassive black hole binaries, and recoiling supermassive black holes. However, many of these sources cannot…
This paper is a brief review of the topic of binary systems as sources of gravitational-wave emission for both LIGO and LISA. In particular I review the current estimates of the associated Galactic event rates and their implications for…
The cores of most galaxies are thought to harbour supermassive black holes, which power galactic nuclei by converting the gravitational energy of accreting matter into radiation (ref 1). Sagittarius A*, the compact source of radio, infrared…
Understanding the interplay between black-hole accretion and star formation, and how to disentangle the two, is crucial to our understanding of galaxy formation and evolution. To investigate, we use a combination of optical and…
The Laser Interferometer Space Antenna (LISA) mission, scheduled for launch in the early 2030s, is a gravitational wave observatory in space designed to detect sources emitting in the milli-Hertz band. In contrast to the present ground…
We investigate the properties of stars born via gravitational instability in accretion discs around supermassive black holes (SMBHs) in active galactic nuclei (AGN), and how this varies with the SMBH mass, accretion rate, or viscosity. We…
Superposition of gravitational waves generated by astrophysical sources is expected to give rise to the stochastic gravitational-wave background. We focus on the background generated by the ring-down of black holes produced in the stellar…
We argue that gravitational instability in the outer parts of collapsar disks may lead to fragmentation near the radius where helium photodisintegrates, because of the strong cooling provided by this process. This physics sets clear…
Strong iron lines are a common feature of the optical spectra of active galactic nuclei (AGNs) and quasars from $z\sim 6-7$ to the local Universe, and [Fe/Mg] ratios do not show cosmic evolution. During active episodes, accretion disks…
A cold neutral and extremely dim accretion disk may be present as a remnant of a past vigorous activity around the black hole in our Galactic Center (GC). Here we discuss ways to detect such a disk through its interaction with numerous…