Gabriel Torok

Radial and vertical epicyclic frequencies of Keplerian motion in the field of Kerr naked singularities. Comparison with the black hole case and possible instability of naked-singularity accretion discs

Relativistic Keplerian orbital frequency (

ON MASS CONSTRAINTS IMPLIED BY THE RELATIVISTIC PRECESSION MODEL OF TWIN-PEAK QUASI-PERIODIC OSCILLATIONS IN CIRCINUS X-1

\nu_{\mathrm{K}}

On the distribution of frequency ratios of kHz quasi-periodic oscillations

) and related epicyclic frequencies (radial

Quasiperiodic oscillations in a strong gravitational field around neutron stars testing braneworld models

\nu_{\mathrm{r}}

Multi-resonance orbital model of high-frequency quasi-periodic oscillations: possible high-precision determination of black hole and neutron star spin

, vertical

Confronting the models of 3:2 quasiperiodic oscillations with the rapid spin of the microquasar GRS 1915+105

\nu_{\theta}

Humpy LNRF-velocity profiles in accretion discs orbiting almost extreme Kerr black holes : A possible relation to quasi-periodic oscillations

) play an important role in the physics of accretion discs orbiting Kerr black holes – quasiperiodic oscillations observed in microquasars can be explained by associated resonant or trapping effects. Because of growing theoretical evidence of the possible existence of naked singularities, we discuss the behaviour of the fundamenal orbital frequencies for Keplerian motion in the field of Kerr naked singularities, primarily in order to find phenomena that could observationally distinguish a hypothetical naked singularity from black holes. Some astrophysically important consequences are sketched, namely the existence of strong resonant frequency for all Kerr naked singularities, with radial and vertical epicyclic frequencies equal and given by the relation

Reversal of the amplitude difference of kHz QPOs in six atoll sources

\omega_\mathrm{sr}\,

QPOs in microquasars and Sgr A.: measuring the black hole spin

=

Internal resonance in nonlinear disk oscillations and the amplitude evolution of neutron-star kilohertz QPOs

\,\,a^{-2}\sqrt {a^2-1}\,(a^2+1 )^{-1}