Publication date: Dec 2014
Abstract:
We study oscillations of an electric current-carrying and axially-
symmetric string loop in the vicinity of a Schwarzschild black hole
embedded in an asymptotically uniform magnetic field. The radial
profiles of frequencies of small oscillations of the string loop around
stable equilibrium points are given for the radial and vertical harmonic
modes that are relevant also in the quasi-periodic stages of the
oscillations. Their properties in dependence on the uniform magnetic
field intensity and angular momentum parameters of the string loops are
determined. We examine the relevance of resonant phenomena of the radial
and vertical string-loop oscillations at their frequency ratio 3:2. The
oscillatory frequencies of the string loops are compared with the
frequencies of high-frequency quasi-periodic oscillations (HF QPOs)
observed in the microquasars GRS 1915+105, XTE 1550-564, GRO 1655-40
containing a black hole. We have demonstrated that the influence of the
uniform magnetic field does not allow us to explain all the observed
data for non-rotating black holes. Clearly, rotation of the black hole
is necessary to explain the all the observed frequencies in the
microquasars by the string loop oscillations.
Authors:
Kološ, Martin; Stuchlík, Zdeněk; Tursunov, Arman;