1304.0584 (Orhan Donmez)

On the development of instability of the black hole-torus systems and
quasi periodic oscillations    [PDF]

Orhan Donmez

We present the numerical study of dynamical instability of a pressure-supported relativistic torus, rotating around the black hole with a constant specific angular momentum on a fixed space-time background, in case of perturbation by a matter coming from the outer boundary. Two dimensional general relativistic hydrodynamical equations are solved at equatorial plane using the HRSCS to study the effect of perturbation on the stable systems. We have found that the perturbed torus creates an instability which causes the gas falling into the black hole in a certain dynamical time. All the models indicate an oscillating torus with certain frequency around their instant equilibrium. The dynamic of accreted torus varies with the size of initial stable torus, black hole spin and other variables, such as Mach number, sound speed, initial radius of the torus etc., but not their instability. The precessing torus not only effects the gravitational radiation, but also generates it. On the other hand, the mass accretion rate is slightly proportional to the torus-to-hole mass ratio in the black hole-torus system, but it strongly depends on inner radius of the torus. Increasing the specific angular momentum of the torus outward can lead a more stable torus. Our numerical simulations also show that the oscillating relativistic torus could be used to explain the multiple peaks observed in the black hole high frequency QPOs, responsible for radiation of X-ray observed by different X-ray telescopes.

View original: http://arxiv.org/abs/1304.0584