Time-scale of twin-peak quasi-periodic oscillations and mass of accreting neutron stars

Török, Gabriel; Goluchová, Kateřina; Šrámková, Eva; Urbanec, Martin; Straub, O.

doi:10.1093/mnras/stz1929

Cited by 21 publications

(12 citation statements)

References 118 publications

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“…The CT model provides generally better fits of the NS data than the RP model. It also predicts a lower NS mass than the RP model which, in some cases, implies a mass estimate that is too high (Török et al 2018(Török et al , 2019.…”

Section: Favoured Modelsmentioning

confidence: 94%

“…sented in the studies of Török et al (2016Török et al ( , 2018Török et al ( , 2019, which is further discussed in Section 7.2. Finally, we also assume a combination of modes that in the slender torus limit leads to the same observable frequencies as the "warped disk" model proposed by Kato (2001Kato ( , 2004 in the context of diskoseismology (the study of oscillations of thin disks).…”

Section: Modelmentioning

confidence: 99%

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Models of high-frequency quasi-periodic oscillations and black hole spin estimates in Galactic microquasars

Kotrlová,

Šrámková,

Török

et al. 2020

Preprint

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We explore the influence of non-geodesic pressure forces that are present in an accretion disk on the frequencies of its axisymmetric and non-axisymmetric epicyclic oscillation modes. We discuss its implications for models of high-frequency quasi-periodic oscillations (QPOs) that have been observed in the X-ray flux of accreting black holes (BHs) in the three Galactic microquasars, GRS 1915+105, GRO J1655−40 and XTE J1550−564. We focus on previously considered QPO models that deal with low azimuthal number epicyclic modes, |m| ≤ 2, and outline the consequences for the estimations of BH spin, a ∈ [0, 1]. For four out of six examined models, we find only small, rather insignificant changes compared to the geodesic case. For the other two models, on the other hand, there is a fair increase of the estimated upper limit on the spin. Regarding the QPO model's falsifiability, we find that one particular model from the examined set is incompatible with the data. If the microquasar's spectral spin estimates that point to a > 0.65 were fully confirmed, two more QPO models would be ruled out. Moreover, if two very different values of the spin, such as a ≈ 0.65 in GRO J1655−40 vs. a ≈ 1 in GRS 1915+105, were confirmed, all the models except one would remain unsupported by our results. Finally, we discuss the implications for a model recently proposed in the context of neutron star (NS) QPOs as a disk-oscillation-based modification of the relativistic precession model. This model provides overall better fits of the NS data and predicts more realistic values of the NS mass compared to the relativistic precession model. We conclude that it also implies a significantly higher upper limit on the microquasar's BH spin (a ∼ 0.75 vs. a ∼ 0.55).

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Section: Favoured Modelsmentioning

confidence: 94%

Section: Modelmentioning

confidence: 99%

Models of high-frequency quasi-periodic oscillations and black hole spin estimates in Galactic microquasars

Kotrlová,

Šrámková,

Török

et al. 2020

Preprint

Self Cite

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“…This finding is rather independent on the NS spin (Török et al 2016a,b). The model also likely predicts a lower NS mass compared to the RP model, which, in some cases, implies a mass estimate that is too high (Török et al 2016a(Török et al , 2018(Török et al , 2019. Moreover, the upper limit on the Galactic microquasars spin given by this model is significantly higher than in the RP model's case, namely j ∼ 0.75 vs. j ∼ 0.55.…”

Section: Qpo Models Under Considerationmentioning

confidence: 79%

“…Having briefly illustrated the large collection of ideas proposed to explain the QPO phenomenon, in this work we focus solely on two particular QPO models. Following our previous study (Török et al 2016a(Török et al ,b, 2018(Török et al , 2019, we derive a simple analytic formula relating the QPO frequencies to parameters of rotating compact objects within the framework of these models. Finally, we apply the formula to data of several NS sources and compare the predictions of the models.…”

Section: Introductionmentioning

confidence: 99%

Simple analytic formula relating the mass and spin of accreting compact objects to their rapid X-ray variability

Török,

Kotrlová,

Matuszková

et al. 2022

Preprint

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Following the previous research on epicyclic oscillations of accretion disks around black holes (BHs) and neutron stars (NSs), a new model of high-frequency quasi-periodic oscillations (QPOs) has been proposed (CT model), which deals with oscillations of fluid in marginally overflowing accretion tori (i.e., tori terminated by cusps). According to preliminary investigations, the model provides better fits of the NS QPO data compared to the relativistic precession (RP) model. It also implies a significantly higher upper limit on the Galactic microquasars BH spin. A short analytic formula has been noticed to well reproduce the model's predictions on the QPO frequencies in Schwarzschild spacetimes. Here we derive an extended version of this formula that applies to rotating compact objects. We start with the consideration of Kerr spacetimes and derive a formula that is not restricted to a particular specific angular momentum distribution of the inner accretion flow, such as Keplerian or constant. Finally, we consider Hartle-Thorne spacetimes and include corrections implied by the NS oblateness. For a particular choice of a single parameter, our relation provides frequencies predicted by the CT model. For another value, it provides frequencies predicted by the RP model. We conclude that the formula is well applicable for rotating oblateness NSs and both models. We briefly illustrate application of our simple formula on several NS sources and confirm the expectation that the CT model is compatible with realistic values of the NS mass and provides better fits of data than the RP model.

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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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Time-scale of twin-peak quasi-periodic oscillations and mass of accreting neutron stars

Cited by 21 publications

References 118 publications

Models of high-frequency quasi-periodic oscillations and black hole spin estimates in Galactic microquasars

Models of high-frequency quasi-periodic oscillations and black hole spin estimates in Galactic microquasars

Simple analytic formula relating the mass and spin of accreting compact objects to their rapid X-ray variability

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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