Untitled

Kato, Takao; Keem, Changho; Ohbuchi, Akira

doi:10.1023/a:1004928524154

Cited by 76 publications

(124 citation statements)

References 10 publications

Supporting

Mentioning

123

Contrasting

Order By: Relevance

“…Overall, the results found indicate that the p-mode oscillations of vertically integrated tori in a Kerr space-time share many of the features already encountered in a Schwarzschild space-time, in particular: the dependence of the fundamental eigenfrequencies on the position of the rest-mass density maximum and on the radial size of the discs; the relation of p modes with the radial epicyclic oscillations of point-like particles; or the simple 2 : 3 harmonic sequence for the lowest-order eigenfrequencies. Furthermore, this work extends to geometrically thick discs all of the relativistic disco-seismology analyses carried so far for thin discs (Okazaki, Kato & Fukue 1987;Perez et al 1997;Silbergleit, Wagoner & Rodriguez 2001;Kato 2001;Rodriguez, Silbergleit & Wagoner 2002).…”

Section: Introductionmentioning

confidence: 74%

Oscillations of vertically integrated relativistic tori - II. Axisymmetric modes in a Kerr space-time

Montero

Rezzolla

Yoshida

2004

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

This is the second in a series of papers investigating the oscillation properties of relativistic, non‐self‐gravitating tori orbiting around black holes. Extending the work done in a Schwarzschild background, here we consider the axisymmetric oscillations of vertically integrated tori in a Kerr space–time. The tori are modelled with a number of different non‐Keplerian distributions of specific angular momentum, and we discuss how the oscillation properties depend on these and on the rotation of the central black hole. We first consider a local analysis to highlight the relations between acoustic and epicyclic oscillations in a Kerr space–time, and subsequently perform a global eigenmode analysis to compute the axisymmetric p modes. In analogy with what has been found in a Schwarzschild background, these modes behave as sound waves that are modified by rotation and are globally trapped in the torus. For constant distributions of specific angular momentum, the eigenfrequencies appear in a sequence 2: 3: 4: … , which is essentially independent of the size of the disc and of the black hole rotation. For non‐constant distributions of angular momentum, on the other hand, the sequence depends on the properties of the disc and on the spin of the black hole, becoming harmonic for sufficiently large tori. We also comment on how p modes could explain the high‐frequency quasi‐periodic oscillations observed in low‐mass X‐ray binaries with a black hole candidate and the properties of an equivalent model in Newtonian physics.

show abstract

Section: Introductionmentioning

confidence: 74%

Oscillations of vertically integrated relativistic tori - II. Axisymmetric modes in a Kerr space-time

Montero

Rezzolla

Yoshida

2004

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…We now discuss the implications of the above results for QPO models. There are two different classes of models of the kHz QPOs: those involving clumps within or above the accretion disc (for a recent review see, for example, Miller, Lamb & Psaltis 1998;Stella & Vietri 1999;van der Klis 2004), and those involving oscillations of the disc (reviewed in Wagoner 1999 andKato 2001).…”

Section: Discussionmentioning

confidence: 99%

On the high coherence of kHz quasi-periodic oscillations

Barret

Kluźniak

Olive

et al. 2005

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We have carried out a systematic study of the properties of the kHz quasi-periodic oscillations (QPOs) observed in the X-ray emission of the neutron star low-mass X-ray binary 4U 160852, using archival data obtained with the Rossi X-ray Timing Explorer. We have investigated the quality factor, Q, of the oscillations (defined as the ratio, /, of the frequency of the QPO peak to its full width at half-maximum ). In order to minimize the effect of long-term frequency drifts, power spectra were computed over the shortest times permitted by the data statistics. We show that the high Q of 200 reported previously for the lower-frequency kHz QPO is by no means exceptional, as we observe a mean Q value in excess of 150 in 14 out of the 21 observations analysed and Q can remain above 200 for thousands of seconds. The frequency of the QPO varies over the wide range 560890 Hz and we find a systematic trend for the coherence time of the QPO, estimated as =Q/() = 1/(), to increase with , up to a maximum level at 800 Hz, beyond which it appears to decrease, at frequencies where the QPO weakens. There is a more complex relationship between and the QPO rms amplitude, in which positive and negative correlations can be found. A higher-frequency QPO, revealed by correcting for the frequency drift of the 560890 Hz one, has a much lower Q (10) which does not follow the same pattern. We discuss these results in the framework of competing QPO models and we show that those involving clumps orbiting within or above the accretion disc are ruled out

show abstract

“…Simulations by Igumenshchev, Chen & Abramowicz (1996) have shown that variability and oscillations can be triggered by viscous processes. Kato (2001) has suggested that energy flux within the disc through viscous and angular momentum processes can alter the equilibrium state, producing oscillations. Finally, in highly dynamical situations, the disc will naturally lack complete azimuthal symmetry (e.g.…”

Section: Localized External Perturbationmentioning

confidence: 99%

Oscillations of thick accretion discs around black holes -- II

Rubio-Herrera¹,

Lee²

2005

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We present a numerical study of the global modes of oscillation of thick accretion discs around black holes. We have previously studied the case of constant distributions of specific angular momentum. In this second paper, we investigate (i) how the size of the disc affects the oscillation eigenfrequencies, and (ii) the effect of power‐law distributions of angular momentum on the oscillations. In particular, we compare the oscillations of the disc with the epicyclic eigenfrequencies of a test particle with different angular momentum distributions orbiting around the central object. We find that there is a frequency shift away from the epicyclic eigenfrequency of the test particle to lower values as the size of the tori is increased. We have also studied the response of a thick accretion disc to a localized external perturbation using non‐constant specific angular momentum distributions within the disc. We find that in this case it is also possible (as reported previously for constant angular momentum distributions) to efficiently excite internal modes of oscillation. In fact, we show here that the local perturbations excite global oscillations (acoustic p modes) closely related to the epicyclic oscillations of test particles. Our results are particularly relevant in the context of low‐mass X‐ray binaries and microquasars, and the high‐frequency quasi‐periodic oscillations observed in them. Our computations make use of a smoothed particle hydrodynamics code in azimuthal symmetry, and use a gravitational potential that mimics the effects of strong gravity.

show abstract

Untitled

Cited by 76 publications

References 10 publications

Oscillations of vertically integrated relativistic tori - II. Axisymmetric modes in a Kerr space-time

Oscillations of vertically integrated relativistic tori - II. Axisymmetric modes in a Kerr space-time

On the high coherence of kHz quasi-periodic oscillations

Oscillations of thick accretion discs around black holes -- II

Contact Info

Product

Resources

About