Constraining Models of Twin-Peak Quasi-Periodic Oscillations With Realistic Neutron Star Equations of State

Török, Gabriel; Goluchová, Kateřina; Urbanec, Martin; Šrámková, Eva; Adámek, Karel; Urbancová, Gabriela; Pecháček, Tomáš; Bakala, Pavel; Stuchlík, Zdeněk; Horák, Jiří; Jurýšek, Jakub

doi:10.3847/1538-4357/833/2/273

Cited by 18 publications

(17 citation statements)

References 90 publications

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“… 2010 ). For a recent work investigating the compatibility of realistic neutron star equations of state with several QPO modes see Török ( 2016 ). Constants of motion in stationary, axisymmetric spacetimes have been investigated recently in Markakis ( 2014 ).…”

Section: Rotating Relativistic Stars In Lmxbsmentioning

confidence: 99%

Rotating stars in relativity

2017

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Rotating relativistic stars have been studied extensively in recent years, both theoretically and observationally, because of the information they might yield about the equation of state of matter at extremely high densities and because they are considered to be promising sources of gravitational waves. The latest theoretical understanding of rotating stars in relativity is reviewed in this updated article. The sections on equilibrium properties and on nonaxisymmetric oscillations and instabilities in f-modes and r-modes have been updated. Several new sections have been added on equilibria in modified theories of gravity, approximate universal relationships, the one-arm spiral instability, on analytic solutions for the exterior spacetime, rotating stars in LMXBs, rotating strange stars, and on rotating stars in numerical relativity including both hydrodynamic and magnetohydrodynamic studies of these objects.

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Section: Rotating Relativistic Stars In Lmxbsmentioning

confidence: 99%

Rotating stars in relativity

2017

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“…A list of individual sources along with a dozen of related references is given in Table 1. Apart from the datapoints, we include in Figure 1a a curve which indicates the trend predicted by the relativistic precession model of HF QPOs -hereafter RP model (see, e.g., Stella & Vietri 1999;Stella & Vietri 2001;Belloni et al 2005;Török et al 2016a). Several attempts to model the individual observed correlations with simple geodesic orbital models or phenomenological relations have failed in the past (e.g., Lin et al 2011;Török et al 2012Török et al , 2016a, and references therein).…”

Section: Behaviour and Fits Of The Frequency Correlationsmentioning

confidence: 99%

“…Apart from the datapoints, we include in Figure 1a a curve which indicates the trend predicted by the relativistic precession model of HF QPOs -hereafter RP model (see, e.g., Stella & Vietri 1999;Stella & Vietri 2001;Belloni et al 2005;Török et al 2016a). Several attempts to model the individual observed correlations with simple geodesic orbital models or phenomenological relations have failed in the past (e.g., Lin et al 2011;Török et al 2012Török et al , 2016a, and references therein). In several particular cases, fits are reliable when two free parameters specific for each source are considered (e.g., Psaltis et al 1998;Abramowicz et al 2005b,a;Zhang 2006), although there are still numerous clear deviations of data from the expected trend.…”

Section: Behaviour and Fits Of The Frequency Correlationsmentioning

confidence: 99%

“…In the series of works (Török et al 2010(Török et al , 2012(Török et al , 2016a) the effective degeneracy between various parameters of several orbital QPO models has been discussed. Within this degeneracy, each combination of NS mass M , angular momentum j and quadrupole moment q corresponds to a certain value of a single generalized parameter M, e.g., non-rotating NS mass.…”

Section: A Simple Formula Reproducing the Individual Correlationsmentioning

confidence: 99%

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On one-parametric formula relating the frequencies of twin-peak quasi-periodic oscillations

Török

Goluchová

Šrámková

et al. 2017

Monthly Notices of the Royal Astronomical Society: Letters

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Twin-peak quasi-periodic oscillations (QPOs) are observed in several low-mass X-ray binary systems containing neutron stars (NSs). Timing analysis of X-ray fluxes of more than dozen of such systems reveals remarkable correlations between the frequencies of two characteristic peaks present in the power density spectra. The individual correlations clearly differ, but they roughly follow a common individual pattern. High values of measured QPO frequencies and strong modulation of the X-ray flux both suggest that the observed correlations are connected to orbital motion in the innermost part of an accretion disc. Several attempts to model these correlations with simple geodesic orbital models or phenomenological relations have failed in the past. We find and explore a surprisingly simple analytic relation that reproduces individual correlations for a group of several sources through a single parameter. When an additional free parameter is considered within our relation, it well reproduces the data of a large group of 14 sources. The very existence and form of this simple relation supports the hypothesis of the orbital origin of QPOs and provides the key for further development of QPO models. We discuss a possible physical interpretation of our relation's parameters and their links to concrete QPO models.

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“…gravitational field and strong magnetic field regions (Miller et al 1998;Lamb & Miller 2001;Abramowicz et al 2003a,b;Zhang 2004), to probe the magnetosphere-disk structure of NS-LMXBs (Wang et al 2018b), and to constrain the NS Mass−Radius relation (Miller & Miller 2015;Török et al 2016Török et al , 2019van Doesburgh et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Kilohertz quasi-periodic oscillations as probes of the X-ray color-color diagram and neutron star accretion-disk structure for Z sources

Wang

Zhang

et al. 2020

A&A

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Based on the detected kilohertz quasi-periodic oscillations (kHz QPOs) in neutron star low-mass X-ray binaries (NS-LMXBs), we investigate the evolution of the NS magnetosphere-disk structure along the Z track in the X-ray color-color diagram (CCD) for luminous Z sources, such as Cyg X-2, GX 5-1, GX 17+2, and Sco X-1. We find that the magnetosphere-disk radius r inferred by kHz QPOs for all the sources shows a monotonically decreasing trend along the Z track from the horizontal branch (HB) to the normal branch (NB), implying that the dominated radiation components may dramatically change as the accretion disk moves toward the NS surface. In addition, the specific radius that corresponds to the HB/NB vertex is found to be around r ∼ 20 km, implying a potential characteristic position of transiting for the X-ray radiation mode. Furthermore, we find that the NBs that occur near the NS surface have a radius of r ∼ 16−20 km, which is systematically smaller than those of HBs that have radii of r ∼ 20−29 km. To interpret the relation between the CCD properties and the special magnetosphere-disk radii of Z sources, we suggest that the magnetic field lines corresponding to NB are “frozen-in” to the plasma, and move further inward with the shrinking of the NS magnetosphere-disk radius and pile up near the NS surface. They then form a strong magnetic field region around r ∼ 16−20 km, where the high magnetic energy density and high plasma mass density may dominate the radiation process in NB.

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Constraining Models of Twin-Peak Quasi-Periodic Oscillations With Realistic Neutron Star Equations of State

Cited by 18 publications

References 90 publications

Rotating stars in relativity

Rotating stars in relativity

On one-parametric formula relating the frequencies of twin-peak quasi-periodic oscillations

Kilohertz quasi-periodic oscillations as probes of the X-ray color-color diagram and neutron star accretion-disk structure for Z sources

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