Publication date: Dec 2014
Abstract:
The current-carrying string loops oscillating around a stable equilibrium position in the Kerr background are considered to explain the twin high-frequency quasiperiodic oscillations (HF QPOs) observed in the low-mass X-ray binary 4U 1636-53 containing a neutron star. The frequencies of the radial and vertical string loop oscillations are governed by the mass and spin parameters of the neutron star, and by the string parameter describing combined effects of its tension and angular momentum. The frequencies of the radial and vertical modes of the string loop oscillations can cover the large scatter of the twin HF QPO data observed in the 4U 1636-53 source, but the estimates of the mass M and spin a of the neutron star are rather high, M ∼2.65 M and a ∼ 0.45, while related to the theory of the neutron star structure. Therefore, the string loop oscillation model in the case of the 4U 1636-53 source requires a correction based on an electrically charged string loop interacting with the magnetic field of the neutron star.
Authors:
Stuchlík, Z.; Kološ, M.;