Rapid X-ray variability

Klis, M. van der

doi:10.1017/cbo9780511536281.003

Cited by 407 publications

(199 citation statements)

References 281 publications

(405 reference statements)

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“…Neutron-star Low Mass X-ray Binaries are usually classified in two classes, the Z and the atoll sources; these names are based on the shape that individual sources describe in the color-color diagrams as a result of changes taking place in the sources (CDs, Hasinger & van der Klis 1989;van der Klis 2005). The atoll sources trace a pattern consisting of a single curved branch (banana branch), together with a smaller "island", while the pattern traced by Z sources is characterized by three branches called horizontal branch, normal branch, and flaring branch, respectively.…”

Section: Introductionmentioning

confidence: 99%

A continuous flaring- to normal-branch transition in Scorpius X-1

Casella

Belloni²,

Stella

2006

A&A

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We report the first resolved rapid transition from a Flaring Branch Oscillation to a Normal Branch Oscillation in the RXTE data of the Z source Sco X-1. The transition took place on a time scale of ∼100 s and was clearly associated to the Normal Branch-Flaring Branch vertex in the color-color diagram. We discuss the results in the context of possible association of the Normal Branch Oscillation with other oscillations known both in Neutron-Star and Black-Hole systems, concentrating on the similarities with the narrow 4-6 Hz oscillations observed at high flux in Black-Hole Candidates.

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Section: Introductionmentioning

confidence: 99%

A continuous flaring- to normal-branch transition in Scorpius X-1

Casella

Belloni²,

Stella

2006

A&A

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“…The frequencies of the kilohertz QPOs detected so far range from ∼1300 Hz in 4U 0614+09 [98] down to ∼10 Hz in Cir X-1 [17]. If, as expected, the frequencies of the highest-frequency kilohertz QPOs reflect the orbital frequencies of gas in the disk near the neutron star [69,97], then in most kilohertz QPO sources gas is orbiting close to the surface of the star. The spin frequencies ν spin of the neutron stars in the kilohertz QPO sources are inferred from the periodic accretion-and nuclear-powered X-ray oscillations of these stars.…”

Section: Introductionmentioning

confidence: 52%

“…Some kilohertz QPOs have relative widths δν QPO /ν QPO 0.005 (see [6,69,96,97,4,5,101]) and the accretion luminosity of a neutron star is typically ∼ 5 times the accretion luminosity of the entire disk [67]. Consequently, even if the emission from the annulus were 100% modulated at the frequency of the kilohertz QPO, which is very unlikely, the relative amplitude of the QPO would be only ∼ 0.005×1/6 ∼ 0.08%, much less that the 2-60 keV relative amplitudes ∼ 15% observed in many kilohertz QPO sources (see, e.g., [69,96,97,101]). …”

Section: Accretion-powered Kilohertz Qposmentioning

confidence: 99%

“…Magnetic fields of this size are weak enough to allow at least a fraction of the accreting gas to remain in orbit as it moves into the strong gravitational and radiation fields of these stars, but strong enough to produce anisotropic X-ray emission, potentially allowing the spin rates of these stars to be determined. The discovery and study using RossiXTE of oscillations in the X-ray emission of the accreting neutron stars in LMXBs, with frequencies comparable to the dynamical frequencies near these stars, has provided an important new tool for studying the strong gravitational and magnetic fields, spin rates, masses, and radii of these stars (for previous reviews, see [50,51,46,96,97]). …”

Section: Introductionmentioning

confidence: 99%

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Accreting Neutron Stars in Low-Mass X-Ray Binary Systems

Lamb

Boutloukos

2008

Astrophysics and Space Science Library

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Summary. Using the Rossi X-ray Timing Explorer (RossiXTE), astronomers have discovered that disk-accreting neutron stars with weak magnetic fields produce three distinct types of high-frequency X-ray oscillations. These oscillations are powered by release of the binding energy of matter falling into the strong gravitational field of the star or by the sudden nuclear burning of matter that has accumulated in the outermost layers of the star. The frequencies of the oscillations reflect the orbital frequencies of gas deep in the gravitational field of the star and/or the spin frequency of the star. These oscillations can therefore be used to explore fundamental physics, such as strong-field gravity and the properties of matter under extreme conditions, and important astrophysical questions, such as the formation and evolution of millisecond pulsars. Observations using RossiXTE have shown that some two dozen neutron stars in low-mass X-ray binary systems have the spin rates and magnetic fields required to become millisecond radio-emitting pulsars when accretion ceases, but that few have spin rates above about 600 Hz. The properties of these stars show that the paucity of spin rates greater than 600 Hz is due in part to the magnetic braking component of the accretion torque and to the limited amount of angular momentum that can be accreted in such systems. Further study will show whether braking by gravitational radiation is also a factor. Analysis of the kilohertz oscillations has provided the first evidence for the existence of the innermost stable circular orbit around dense relativistic stars that is predicted by strong-field general relativity. It has also greatly narrowed the possible descriptions of ultradense matter.

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“…In the last few years many kHz QPOs have been detected in the light curves of about 20 neutron star and few black hole sources (for a recent review, see van der Klis 2004). The nature of these QPOs is one of the mysteries which still puzzle and intrigue astrophysicists: apart from giving important insights into the disk structure and the mass and spin of the central object (e.g.…”

Section: Introductionmentioning

confidence: 99%

Stochastic modeling of kHz quasi-periodic oscillation light curves

Vio¹,

Rebusco

Andreani³

et al. 2006

A&A

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Aims. Kluźniak & Abramowicz explain the high frequency, double peak, "3:2" QPOs observed in neutron star and black hole sources in terms of a non-linear parametric resonance between radial and vertical epicyclic oscillations of an almost Keplerian accretion disk. The 3:2 ratio of epicyclic frequencies occurs only in strong gravity. Recently, a simple model incorporating their suggestion was studied analytically: the result is that a small forcing may indeed excite the parametric 3:2 resonance. However, no explanation has been provided on the nature of the forcing which is given an "ad hoc" deterministic form. Methods. In the present paper the same model is considered. The equation are numerically integrated, dropping the ad hoc forcing and adding instead a stochastic term to mimic the action of the very complex processes that occur in accretion disks as, for example, MRI turbulence. Results. We demonstrate that the presence of the stochastic term is able to trigger the resonance in epicyclic oscillations of nearly Keplerian disks, and it influences their pattern.

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Rapid X-ray variability

Abstract: 1 The radius of a zero angular-momentum black hole, R Schw = 2rg = 2GM/c 2 ≈ 3 km M/M ⊙ .

Cited by 407 publications

References 281 publications

A continuous flaring- to normal-branch transition in Scorpius X-1

A continuous flaring- to normal-branch transition in Scorpius X-1

Accreting Neutron Stars in Low-Mass X-Ray Binary Systems

Stochastic modeling of kHz quasi-periodic oscillation light curves

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