| 1. |
- Abramowicz, Marek A, 1945, et al.
(författare)
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The importance of discovering A 3:2 twin-peak quasi-periodic oscillation in an ultraluminous X-ray source, or how to solve the puzzle of intermediate-mass black holes
- 2004
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Ingår i: Astrophysical Journal, Letters. - 0067-0049. ; 609:2
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Tidskriftsartikel (refereegranskat)abstract
- Recently, twin-peak quasi-periodic oscillations (QPOs) have been observed in a 3:2 ratio for three Galactic black hole microquasars with frequencies that have been shown to scale as 1/M, as expected for general relativistic motion near a black hole. It may be possible to extend this result to distinguish between the following two disparate models that have been proposed for the puzzling ultraluminous X-ray sources (ULXs): (1) an intermediate-mass black hole (M~103 M⊙) radiating very near the Eddington limit and (2) a conventional black hole (M~10 M⊙) accreting at a highly super-Eddington rate with its emission beamed along the rotation axis. We suggest that one could discriminate between these models by detecting the counterpart of a Galactic twin-peak QPO in a ULX: the expected frequency for the intermediate-mass black hole model is only about 1 Hz, whereas for the conventional black hole model the expected frequency would be the ~100 Hz value observed for the Galactic microquasars.
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| 2. |
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| 3. |
- Abramowicz, Marek A, 1945, et al.
(författare)
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Interpreting black hole QPOs
- 2004
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Ingår i: AIP Conference Proceedings. - 0094-243X. ; 714, s. 21-28
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- n all the microquasars with two hHz QPOs, the ratio of the frequencies is 3:2, supporting our suggestion that a non-linear resonance between two modes of oscillation in the accretion disk plays a role in exciting the observed modulations of the X-ray flux. We discuss the evidence in favor of this interpretation, and we relate the black hole spin to the frequencies expected for various types of resonances that may occur in nearly Keplerian disks in strong gravity. For those microquasars where the mass of the central X-ray source is known, the black hole spin can be deduced from a comparison of the observed and expected frequencies.
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| 4. |
- Abramowicz, Marek A, 1945, et al.
(författare)
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Twin peak QPOs frequencies in microquasars and Sgr A*. The resonance and other orbital models
- 2004
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Ingår i: Proceedings of RAGtime 4/5 Workshops on black holes and neutron stars, 14-16/13-15 October 2002/2003. - 8072482424
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In all four microquasars which show twin peak kHz QPOs, the ratio of the two frequencies is 3:2. This rather strongly supports the suggestion by Abramowicz, M. A. and Kluzniak [W. Abramowicz, M. A. and Kluzniak, W., (2001). A precise determination of black hole spin in GRO J1655-40. Astronomy and Astrophysics, 374:L19] that twin peak kHz QPOs are due to a resonance between some modes of accretion disk oscillations. Detailed studies of this suggestion revealed that several such non-linear resonances are present in nearly Keplerian disks in strong gravity. Here, we fit to observations predictions of the resonance hypothesis for two particular types of non-linear resonances between vertical and radial epicyclic frequencies. For three microquasars with known masses, the fits give an accurate estimate of the spin.
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| 5. |
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| 6. |
- Horák, Jíri, et al.
(författare)
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Of NBOs and kHz QPOs: a Low-Frequency Modulation in Resonant Oscillations of Relativistic Accretion Disks
- 2004
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Ingår i: Publications of the Astronomical Society of Japan. - 0004-6264. ; 56:5, s. 819-822
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Tidskriftsartikel (refereegranskat)abstract
- The origin of quasi-periodic modulations of flux in the kilohertz range (kHz QPOs), observed in low-mass X-ray binaries, is usually assumed to be physically distinct from that of the "normal branch oscillations" (NBOs) in the Z-sources. We show that a low-frequency modulation of the kHz QPOs is a natural consequence of the non-linear relativistic resonance suggested previously to explain the properties of the high-frequency twin peaks. The theoretical results discussed here are reminiscent of the 6 Hz variations of frequency and amplitude of the kHz QPOs reported by Yu, van der Klis, and Jonker (2001).
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| 7. |
- Kluzniak, Wlodek, et al.
(författare)
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High-frequency QPOs as a problem in physics: non-linear resonance
- 2004
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Ingår i: AIP Conference Proceedings. - 0094-243X. ; 714, s. 379-382
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The presence of a kHz frequency in LMXBs has been expected from scaling laws, by analogy with the QPO phenomenon in HMXB X-ray pulsars. Interpretation of the two kHz frequencies, observed in accreting neutron stars, in terms of non-linear resonance in strong-field gravity led to the prediction of twin QPOs in black hole systems, in a definite frequency ratio (such as 2/3). The imprint of a subharmonic of the 401 Hz rotation rate in the frequencies of the QPOs detected in the accreting millisecond pulsar is at once a signature of non-linear resonance and of coupling between accretion disk modes and the neutron star spin.
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| 8. |
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| 9. |
- Lee, William H., et al.
(författare)
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Resonance in forced oscillations of an accretion disk and kilohertz quasi-periodic oscillations
- 2004
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Ingår i: Astrophysical Journal, Letters. - 0067-0049. ; 603:2
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Tidskriftsartikel (refereegranskat)abstract
- We have performed numerical simulations of a radially perturbed "accretion" torus around a black hole or neutron star and find that the torus performs radial and vertical motions at the appropriate epicyclic frequencies. We find clear evidence that vertical motions are excited in a nonlinear resonance when the applied perturbation is periodic in time. The strongest resonant response occurs when the frequency difference of the two oscillations is equal to one-half of the forcing frequency, precisely as recently observed in the accreting pulsar SAX J1808.4-3658, where the observed kilohertz quasi-periodic oscillation peak separation is half the spin frequency of 401 Hz.
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