Stochastic modeling of kHz quasi-periodic oscillation light curves

Vio, R.; Rebusco, P.; Andreani, P.; Madsen, Henrik; Overgaard, Rune Viig

doi:10.1051/0004-6361:20054432

Cited by 11 publications

(16 citation statements)

References 26 publications

(29 reference statements)

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“…This turbulence generates the radial transport of angular momentum that drives the accretion and heats the disc, but its role in other aspects of the dynamics of accretion discs has hardly been explored though. Vio et al (2006) have recently studied how stochastic processes can produce resonances between the epicyclic modes in an almost Keplerian disc.…”

Section: Epicyclic Oscillationsmentioning

confidence: 99%

Oscillations of tori in the pseudo-Newtonian potential

Šrámková¹,

Torkelsson

Abramowicz

2007

A&A

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Context. The high-frequency quasi-periodic oscillations (HF QPOs) in neutron star and stellar-mass black hole X-ray binaries may be the result of a resonance between the radial and vertical epicyclic oscillations in strong gravity. Aims. In this paper we investigate the resonant coupling between the epicyclic modes in a torus in a strong gravitational field. Methods. We perform numerical simulations of axisymmetric constant angular momentum tori in the pseudo-Newtonian potential. The epicyclic motion is excited by adding a constant radial velocity to the torus. Results. We verify that slender tori perform epicyclic motions at the frequencies of free particles, but the epicyclic frequencies decrease as the tori grow thicker. More importantly, and in contrast to previous numerical studies, we do not find a coupling between the radial and vertical epicyclic motions. The appearance of other modes than the radial epicyclic motion in our simulations is rather due to small numerical deviations from exact equilibrium in the initial state of our torus. Conclusions. We find that there is no pressure coupling between the two axisymmetric epicyclic modes as long as the torus is symmetric with respect to the equatorial plane. However we also find that there are other modes in the disc that may be more attractive for explaining the HF QPOs.

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Section: Epicyclic Oscillationsmentioning

confidence: 99%

Oscillations of tori in the pseudo-Newtonian potential

Šrámková¹,

Torkelsson

Abramowicz

2007

A&A

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“…Since the orbital frequencies of high frequency QPOs lie in the range of orbital frequencies of geodesics just few Schwarzschild radii outside the central massive source [45]. This observation strongly suggest that the QPOs could be related to the orbital motion of particles in an accretion disk [46].…”

Section: Discussion and Final Remarksmentioning

confidence: 80%

“…An interesting theoretical model explaining the QPO properties is the Abramowicz-Kluzniak resonance model [47], which starts from pointing out the importance of the observed 3:2 frequency ratio, and that the commensurability of frequencies may be a clear signature of the existence of resonance in the astrophysical system. From observational point of view the fact that for kHz QPOs the frequencies scale with 1/M, where M is the mass of the central object, provide a strong support to the idea that they are due to orbital oscillations [45]. By adopting the above approach it follows that from a mathematical point of view QPOs can be modeled by analyzing the time evolution of perturbed nearby Keplerian geodesics, which can be described by the equations [45] …”

Section: Discussion and Final Remarksmentioning

confidence: 91%

Electromagnetic radiation of charged particles in stochastic motion

Harkó¹,

Mocanu²

2016

Eur. Phys. J. C

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The study of the Brownian motion of a charged particle in electric and magnetic fields has many important applications in plasma and heavy ions physics, as well as in astrophysics. In the present paper we consider the electromagnetic radiation properties of a charged non-relativistic particle in the presence of electric and magnetic fields, of an exterior non-electromagnetic potential, and of a friction and stochastic force, respectively. We describe the motion of the charged particle by a Langevin and generalized Langevin type stochastic differential equation. We investigate in detail the cases of the Brownian motion with or without memory in a constant electric field, in the presence of an external harmonic potential, and of a constant magnetic field. In all cases the corresponding Langevin equations are solved numerically, and a full description of the spectrum of the emitted radiation and of the physical properties of the motion is obtained. The power spectral density of the emitted power is also obtained for each case, and, for all considered oscillating systems, it shows the presence of peaks, corresponding to certain intervals of the frequency.

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“…This hypothesis is widely discussed (e.g., Abramowicz et al 2002;Horák 2004Horák , 2005bvan der Klis 2005;Vio et al 2006;Rebusco 2008;Reynolds & Miller 2009, among the other references in this paper). It assumes that the resonant modes have eigenfrequencies equal to radial and vertical epicyclic frequency of geodesic orbital motion given by…”

Section: Epicyclic Resonancementioning

confidence: 71%

Disc-oscillation resonance and neutron star QPOs: 3:2 epicyclic orbital model

Urbanec

Török

Šrámková

et al. 2010

A&A

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The high-frequency quasi-periodic oscillations (HF QPOs) that appear in the X-ray fluxes of low-mass X-ray binaries remain an unexplained phenomenon. Among other ideas, it has been suggested that a non-linear resonance between two oscillation modes in an accretion disc orbiting either a black hole or a neutron star plays a role in exciting the observed modulation. Several possible resonances have been discussed. A particular model assumes resonances in which the disc-oscillation modes have the eigenfrequencies equal to the radial and vertical epicyclic frequencies of geodesic orbital motion. This model has been discussed for black hole microquasar sources as well as for a group of neutron star sources. Assuming several neutron (strange) star equations of state and Hartle-Thorne geometry of rotating stars, we briefly compare the frequencies expected from the model to those observed. Our comparison implies that the inferred neutron star radius R NS is larger than the related radius of the marginally stable circular orbit r ms for nuclear matter equations of state and spin frequencies up to 800 Hz. For the same range of spin and a strange star (MIT) equation of state, the inferrred radius is R NS ∼ r ms . The "Paczyński modulation" mechanism considered within the model requires that R NS < r ms . However, we find this condition to be fulfilled only for the strange matter equation of state, masses below 1 M , and spin frequencies above 800 Hz. This result most likely falsifies the postulation of the neutron star 3:2 resonant eigenfrequencies being equal to the frequencies of geodesic radial and vertical epicyclic modes. We suggest that the 3:2 epicyclic modes could stay among the possible choices only if a fairly non-geodesic accretion flow is assumed, or if a different modulation mechanism operates.

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Stochastic modeling of kHz quasi-periodic oscillation light curves

Cited by 11 publications

References 26 publications

Oscillations of tori in the pseudo-Newtonian potential

Oscillations of tori in the pseudo-Newtonian potential

Electromagnetic radiation of charged particles in stochastic motion

Disc-oscillation resonance and neutron star QPOs: 3:2 epicyclic orbital model

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