Related papers: Spinning super-massive objects in galactic nuclei …
We present new proper motion measurements and simultaneous orbital solutions for three newly identified (S0-16, S0-19, and S0-20) and four previously known (S0-1, S0-2, S0-4, and S0-5) stars at the Galactic Center. This analysis pinpoints…
We derive closed formulas for the mass and spin parameters of a Kerr black hole in terms of a minimal quantity of observational data: the red-/blue-shifts of photons emitted by massive particles (stars) moving on geodesics around the black…
Accretion of gas onto a central supermassive black hole is generally accepted to be the source of the emitted energy in active galactic nuclei.The broad emission lines we observe in their optical spectra are probably formed in the wind of…
It is widely believed that the spin of black holes in X-ray binaries is mainly natal. A significant spin-up from accretion is not possible. If the secondary has a low mass, the black hole spin cannot change too much even if the black hole…
The spins of ten stellar black holes have been measured using the continuum-fitting method. These black holes are located in two distinct classes of X-ray binary systems, one that is persistently X-ray bright and another that is transient.…
Supermassive black hole binaries are likely to accrete interstellar gas through a circumbinary disk. Shortly before merger, the inner portions of this circumbinary disk are subject to general relativistic effects. To study this regime, we…
The gravitational waves and energy radiations from a spinning compact object with stellar mass in a circular orbit in the equatorial plane of a supermassive Kerr black hole are investigated in this paper. The effect how the spin acts on…
The inner few parsecs at the Galactic Center have come under intense scrutiny in recent years, in part due to the exciting broad-band observations of this region, but also because of the growing interest from theorists motivated to study…
It has recently been pointed out that the spinning Kerr black hole with maximal spin could act as a particle collider with arbitrarily high center-of-mass energy. In this paper, we will extend the result to the charged spinning black hole,…
An outstanding prediction of general relativity is the fact that the angular momentum $S$ of an isolated black hole with mass $\mu$ is limited by the Kerr bound, $S\leq G\mu^2/c$. Testing this cornerstone is challenging due to the…
We study the process of spinning up black holes by accretion from slim disks in a wide range of accretion rates. We show that for super-Eddington accretion rates and low values of the viscosity parameter alpha (\lesssim 0.01) the limiting…
Under the assumption that jets in active galactic nuclei are powered by accretion and the spin of the central supermassive black hole, we are able to reproduce the radio luminosity functions of high- and low-excitation galaxies.…
The $5 - 20 M_\odot$ dark objects in X-ray binary systems and the $10^5 - 10^9 M_\odot$ dark objects in galactic nuclei are currently thought to be the Kerr black holes predicted by General Relativity. However, direct observational evidence…
In this paper, we continue our study of the motion of spinning test bodies orbiting Kerr black holes. Non-spinning test bodies follow geodesics of the spacetime in which they move. A test body's spin couples to the curvature of that…
General relativity limits the compactness of static stars. If the pressure of the fluid is positive and the density decreases with distance from the center, the value of the circumferential radius of the star must be greater than (9/4) G…
It has recently been pointed out that particles falling freely from rest at infinity outside a Kerr black hole can in principle collide with arbitrarily high center of mass energy in the limiting case of maximal black hole spin. Here we aim…
Astronomers have discovered two populations of black holes: (i) stellar-mass black holes with masses in the range 5 to 30 solar masses, millions of which are present in each galaxy in the universe, and (ii) supermassive black holes with…
The nature of the super-massive black hole candidates in galactic nuclei can be tested by analyzing the profile of the K$\alpha$ iron line observed in their X-ray spectrum. In this paper, we consider the possibility that the spacetime in…
We investigate a mechanism for a super-massive black hole at the center of a galaxy to wander in the nucleus region. A situation is supposed in which the central black hole tends to move by the gravitational attractions from the nearby…
We consider the motion of charged and spinning bodies on the symmetry axis of a non-extremal Kerr-Newman black hole. If one treats the body as a test point particle of mass, $m$, charge $q$, and spin $S$, then by dropping the body into the…