scholarly journals The Beat Frequency Model for QPOs

1987 ◽  
Vol 125 ◽  
pp. 347-361 ◽  
Author(s):  
Jacob Shaham
Keyword(s):  
Beat Frequency ◽  
Periodic Oscillation ◽  
The Other ◽  
Prime Model ◽  
Single Model ◽  
Frequency Model ◽  
Quasi Periodic Oscillation ◽  
X Ray ◽  
Low Mass ◽  
X Ray Binaries

We have to date reports of Quasi-Periodic-Oscillation (QPO) observations in some twelve X-ray source, of which at least seven are low mass X-ray binaries (van der Klis 1987). They constitute a formidable zoo of phenomenae with so much variety that they, at times, do not at all even seem amenable to a single model. Some of the other QPO talks in these proceedings will try and present observations in the context of various models. My task is to talk about the Beat Frequency Model which, it seems to me, is by far the prime model for at least some of the QPOs.

scholarly journals Millisecond Time Variations of X-Ray Binaries

1998 ◽  
Vol 188 ◽  
pp. 107-110
Author(s):  
J. H. Swank
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Beat Frequency ◽  
Rotation Period ◽  
Periodic Oscillation ◽  
Frequency Model ◽  
X Ray ◽  
Low Mass ◽  
The Difference ◽  
X Ray Binaries

Millisecond time-scales are natural for some neutron star and black hole processes, although possibly difficult to observe. The Rossi X-Ray Timing Explorer (RXTE) has found that for the neutron stars in low-mass X-ray binaries (LMXB) there are flux oscillations at high frequencies, with large amplitudes. Z sources and bursters tend to exhibit oscillations in the range 300-1200 Hz. Persistent emission may exhibit one or both of two features. In bursts from different bursters, a nearly coherent pulsation is seen, which may be the rotation period of the neutron star. For some the frequency equals the difference between the two higher frequencies, suggesting a beat frequency model, but in others it is twice the difference. The sources span two orders of magnitude in accretion rate, yet the properties are similar. The similar maximum frequencies suggests that it corresponds to the Kepler orbit frequency at the minimum stable orbit or the neutron star surface, either of which would determine the neutron star masses, radii and equation of state. Theories of accretion onto black holes predict a quasi-periodic oscillation (QPO) related to the inner accretion disk. The two microquasar black hole candidates (BHCs) have exhibited candidates for this or related frequencies.

scholarly journals Kilohertz QPO in Low Mass X-Ray Binaries: an Overview

1997 ◽  
Vol 163 ◽  
pp. 347-350
Author(s):  
M. van der Klis
Keyword(s):  
Beat Frequency ◽  
Current Status ◽  
Frequency Model ◽  
Periodic Oscillations ◽  
Simple Interpretation ◽  
X Ray ◽  
Peak Separation ◽  
Low Mass ◽  
The Difference ◽  
X Ray Binaries

AbstractI review the current status of the investigations of the kilohertz quasi-periodic oscillations that have been discovered in low-mass Xray binaries (LMXBs) with NASA’s Rossi X-ray Timing Explorer (RXTE) since February 1996. Seven sources have now shown this new phenomenon, one Z source (Sco X–l) and 6 atoll sources (all X-ray bursters), and some patterns are beginning to emerge. The frequencies of the oscillations are between 500 and 1200 Hz. They can be coherent for more than 102 cycles, but a more typical coherence is several 101. Amplitudes are between 0.5 and 16% (rms) of the total flux. Most sources show double kHz peaks separated by a few 102 Hz, which move up and down in frequency together. In Sco X–l the peak frequencies systematically increase, and the peak separation systematically decreases, with Ṁ. In 4U 1728–34 a third oscillation is seen at a frequency equal to the difference frequency of the two kHz peaks, but only during X-ray bursts. A simple interpretation in terms of a beat-frequency model with the difference frequency being the neutron star’s spin, as suggested by this result, is inconsistent with the fact that in Sco X–l the peak separation varies.

scholarly journals Distribution of twin kHz QPOs in LMXBs

2012 ◽  
Vol 8 (S290) ◽  
pp. 327-328
Author(s):  
D. H. Wang ◽  
L. Chen
Keyword(s):  
Common Property ◽  
Periodic Oscillation ◽  
Quasi Periodic Oscillation ◽  
Mean Values ◽  
Orbital Frequency ◽  
Low Mass ◽  
The Common ◽  
The Mean ◽  
X Ray Binaries ◽  
Z Sources

AbstractWith kilohertz quasi-periodic oscillation (kHz QPO) sources in neutron star low mass X-ray binaries (NS-LMXBs) published up to now, we analyze the centroid frequency (ν) distribution of twin kHz QPOs. We find that Atoll and Z sources show the similar distributions of ν1 and ν2, which indicate that twin kHz QPOs may be the common property of NS-LXMBs and have the similar physical origins. The mean values of ν1 and ν2 in Atoll sources are higher than those in Z sources, and we consider that this may because the QPO signals are sheltered by the thicken accretion disk or corona in Z sources. The maximums of ν2 in both Atoll and Z sources are the same order as the Keplerian orbital frequency of the NS surface, so kHz QPOs could occur near the NS surface.

scholarly journals The Beat-Frequency Interpretation of Kilohertz Quasi-periodic Oscillations in Neutron Star Low-Mass X-Ray Binaries

1998 ◽  
Vol 501 (1) ◽  
pp. L95-L99 ◽  
Author(s):  
Dimitrios Psaltis ◽  
Mariano Méndez ◽  
Rudy Wijnands ◽  
Jeroen Homan ◽  
Peter G. Jonker ◽  
...  
Keyword(s):  
Neutron Star ◽  
Beat Frequency ◽  
Periodic Oscillations ◽  
X Ray ◽  
Frequency Interpretation ◽  
Low Mass ◽  
X Ray Binaries

Discovery of an ∼7 H[CLC]z[/CLC] Quasi-periodic Oscillation in the Low-Luminosity Low-Mass X-Ray Binary 4U 1820−30

1999 ◽  
Vol 512 (1) ◽  
pp. L39-L42 ◽  
Author(s):  
Rudy Wijnands ◽  
Michiel van der Klis ◽  
Erik-Jan Rijkhorst
Keyword(s):  
Periodic Oscillation ◽  
Quasi Periodic Oscillation ◽  
X Ray ◽  
Low Mass

The parallel tracks of kHz QPOs in low-mass X-ray binary 4U 1728−34: explorer of the bimodal accretion modes

2020 ◽  
Vol 497 (3) ◽  
pp. 2893-2898
Author(s):  
De-Hua Wang ◽  
Cheng-Min Zhang
Keyword(s):  
Neutron Star ◽  
Accretion Rate ◽  
Periodic Oscillation ◽  
Quasi Periodic Oscillation ◽  
X Ray ◽  
Parallel Track ◽  
Theoretical Assumptions ◽  
Low Mass

ABSTRACT Parallel tracks in the relation between the lower kilohertz quasi-periodic oscillation (kHz QPO) frequency ν1 and the X-ray intensity I have been observed in the neutron star low-mass X-ray binary (NS-LMXB) 4U 1728−34, and we try to ascribe these phenomena to the bimodal accretion modes, i.e. the disc accretion and radial accretion. For the source with one constant radial accretion rate $\dot{M}_{\rm r}$, as the increase of the disc accretion rate $\dot{M}_{\rm d}$, the NS magnetosphere-disc radius can shrink from ∼18 to ∼16 km, while ν1 increases from ∼670 to ∼870 Hz. Then, due to the increase of the kHz QPO frequency and total X-ray intensity Itot, the source will trace out an oblique track in ν1–I relation. While, if the source enters another constant radial accretion rate due to the variation of the accretion environment, the increase of the disc accretion rate can arise another parallel track in ν1–I relation. Finally, the reliability of the theoretical assumptions, the variability of the accretion radius and accretion rate, as well as the dependence of the two accretion modes, are also investigated and discussed.

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