A NEW CORRELATION WITH LOWER KILOHERTZ QUASI-PERIODIC OSCILLATION FREQUENCY IN THE ENSEMBLE OF 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.

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Search for intermittent X-ray pulsations from neutron stars in low-mass X-ray binaries

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2021.6 ◽

2021 ◽

Vol 38 ◽

Author(s):

Yunus Emre Bahar ◽

Manoneeta Chakraborty ◽

Ersin Göğüş

Keyword(s):

Neutron Stars ◽

Orbital Period ◽

Oscillation Frequency ◽

Orbital Motion ◽

X Rays ◽

X Ray ◽

Second Stage ◽

Corrected Data ◽

Low Mass ◽

X Ray Binaries

Abstract We present the results of our extensive binary orbital motion corrected pulsation search for 13 low-mass X-ray binaries. These selected sources exhibit burst oscillations in X-rays with frequencies ranging from 45 to 1 122 Hz and have a binary orbital period varying from 2.1 to 18.9 h. We first determined episodes that contain weak pulsations around the burst oscillation frequency by searching all archival Rossi X-ray Timing Explorer data of these sources. Then, we applied Doppler corrections to these pulsation episodes to discard the smearing effect of the binary orbital motion and searched for recovered pulsations at the second stage. Here we report 75 pulsation episodes that contain weak but coherent pulsations around the burst oscillation frequency. Furthermore, we report eight new episodes that show relatively strong pulsations in the binary orbital motion corrected data.

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Distribution of twin kHz QPOs in LMXBs

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312020248 ◽

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.

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

The Astrophysical Journal ◽

10.1086/311872 ◽

1999 ◽

Vol 512 (1) ◽

pp. L39-L42 ◽

Cited By ~ 29

Author(s):

Rudy Wijnands ◽

Michiel van der Klis ◽

Erik-Jan Rijkhorst

Keyword(s):

Periodic Oscillation ◽

Quasi Periodic Oscillation ◽

X Ray ◽

Low Mass

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

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2161 ◽

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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