High frequency QPOs, nonlinear oscillations in strong gravity

Kluźniak, W.

doi:10.1002/asna.200510420

Cited by 19 publications

(21 citation statements)

References 16 publications

(23 reference statements)

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“…In addition to the accretion inflow, outflows are present, in microquasars often in the form of transient, well collimated 3 / 2 3 / 2 1655 (online colour at www.an-journal.org) The above "Bursa plot" illustrates a rather encouraging qualitative agreement between the twin peak QPO observations (Barret, Olive & Coleman Miller 2005;van der Klis 2005) and the theoretical model based on a non-linear, stronggravity resonance (Kluźniak 2005). Characteristically for a non-linear resonance (for which a resonance range ∆ν ∼ ν A 1+|p| depends on the amplitude A), the observed ratios of frequencies wander around the exact 3/2 value, determined directly by the strong gravity.…”

supporting

confidence: 61%

QPO as the Rosetta Stone for understanding black hole accretion

Abramowicz

2005

Astron Nachr

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Quasi periodic oscillations (QPO) seen in the X-ray fluxes of individual neutron stars and black hole sources are one of most intriguing phenomena in today's astrophysics. The QPO nature is visibly determined by super-strong Einstein's gravity. I argue here that it also profoundly depends on the MRI turbulence in accretion flows. Understanding the QPO physics may therefore guide accretion theory out of its present state of confusion.Comment: 5 pages, 2 figure

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supporting

confidence: 61%

QPO as the Rosetta Stone for understanding black hole accretion

Abramowicz

2005

Astron Nachr

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“…(4) As known, various bands of QPO frequencies in BH-LMXBs and NS-LMXBs follow the tight relations (Belloni et al 2005(Belloni et al , 2007, and a pair of high frequency QPOs in stellar and intermediate black hole binaries follows, approximately, a 3:2 ratio relation, which may be the particular phenomena from the innermost stable circular orbit (Abramowicz et al 2003a,b;Pasham et al 2014). In fact, there has been a suggestion in the literature for the 3:2 ratio as a parametric resonance between two particular modes of torus oscillations (Bursa et al 2004;Kluźniak 2005;Kluźniak et al 2007). However, we find that the distribution of the ratio of ν2 to ν1 of the 12 NS-LMXBs sources cluster around the value of ∼ 3 : 2 (see Fig.3 (a)), which shows no obvious correlation with NS spin.…”

Section: Discussionmentioning

confidence: 96%

Correlations between the frequencies of twin kHz QPOs and spins of neutron stars in LMXBs

Wang

Zhang

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We investigate the correlation between the frequencies of the twin kilohertz quasiperiodic oscillations (kHz QPOs) and the neutron star (NS) spins in low mass X-ray binaries (LMXBs), based on the data sets of 12 sources with simultaneously detected twin kHz QPOs and NS spins, and find that the histogram of the ratio between the frequency difference of twin kHz QPOs (∆ν ≡ ν 2 − ν 1 ) and NS spin ν s shows a nonuniform distribution with a gap at ∆ν/ν s ∼ 0.65. We try to classify the 12 sources into two categories according to this gap: (I) The slow rotators with ν s ∼ 311 Hz, XTE J1807.4-294, 4U 1915-05, IGR J17191-2821, 4U 1702-43, 4U 1728-34 and 4U 0614+09 follow a relation ∆ν/ν s > 0.65; (II) The fast rotators with ν s ∼ 546 Hz, SAX J1808.4-3658, KS 1731-260, Aql X-1, 4U 1636-53, SAX J1750.8-2900 and 4U 1608-52 satisfy the relation ∆ν/ν s < 0.65. However, the linear fittings of ∆ν versus ν s relations of group (I) and (II) are unsatisfactory to ensure any certain correlations. We suggest that this phenomenon may arise from the fact that most measured kHz QPOs and spins satisfy the conditions of 1.1 ν s ν 2 < 1300 Hz and ∆ν decreasing with ν 2 . Apparently, the diversified distribution of ∆ν/ν s refutes the simple beatfrequency model, and the statistical correlations between the twin kHz QPOs and NS spins may arise from the magnetosphere-disk boundary environments, e.g., co-rotation radius and NS radius, that modulate the occurrences of X-ray signals. Furthermore, we also find that the distribution of the ratio of ν 2 to ν 1 clusters around the value of ν 2 /ν 1 ∼ 3 : 2, which shows no obvious correlation with NS spins.

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“…We are now explaining these effects by considering the epicyclic frequencies of circular orbits around rotating SQSs, and we extended our numerical investigation to low-mass models to compare our results with the Newtonian theory of rapidly rotating figures of equilibrium. The orbital and epicyclic frequencies are of great interest in the context of x-ray observation of highfrequency variability of emission, specifically of the kHz QPOs [14,[20][21][22][23]42,[44][45][46][47].…”

Section: Discussionmentioning

confidence: 99%

Epicyclic frequencies for rotating strange quark stars: Importance of stellar oblateness

et al. 2014

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Kilohertz quasi periodic oscillations (QPOs) can be used as a probe of the inner regions of accretion disks in compact stars and hence also of the properties of the central object. Most models of kHz QPOs involve epicyclic frequencies to explain their origin. We compute the epicyclic frequencies of nearly circular orbits around rotating strange quark stars. The MIT bag model is used to model the equation of state of quark matter, and the uniformly rotating stellar configurations are computed in full general relativity. The vertical epicyclic frequency and the related nodal precession rate of inclined orbits are very sensitive to the oblateness of the rotating star. For rotating stellar models of moderate and high-mass strange stars, the sense of the nodal precession changes at a certain rotation rate. At lower stellar rotation rates, the orbital nodal precession is prograde, as it is in the Kerr metric, while at higher rotation rates, the precession is retrograde, as it is for Maclaurin spheroids. Thus, qualitatively, the orbits around rapidly rotating strange quark stars are affected more strongly by the effects of stellar oblateness than by the effects of general relativity. We show that epicyclic and orbital frequencies calculated numerically for small mass strange stars are in very good agreement with analytical formulas for Maclaurin spheroids.

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High frequency QPOs, nonlinear oscillations in strong gravity

Abstract: Abstract. Some of the more promising ideas about the origin of the high frequency variability (kHz QPOs) in the observed X-ray emissions of low-mass X-ray binaries are contrasted with less promising ones.

Cited by 19 publications

References 16 publications

QPO as the Rosetta Stone for understanding black hole accretion

QPO as the Rosetta Stone for understanding black hole accretion

Correlations between the frequencies of twin kHz QPOs and spins of neutron stars in LMXBs

Epicyclic frequencies for rotating strange quark stars: Importance of stellar oblateness

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