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    Constraining models of twin peak quasi-periodic oscillations with realistic neutron star equations of state

    Zdeněk Stuchlík · 01 listopadu, 2016 · Fyzika · 0 comments
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    Publication date: Nov 2016

    Abstract:
    Twin-peak quasi-periodic oscillations (QPOs) are observed in the X-ray
    power-density spectra of several accreting low-mass neutron star (NS)
    binaries. In our previous work we have considered several QPO models. We
    have identified and explored mass-angular-momentum relations implied by
    individual QPO models for the atoll source 4U 1636-53. In this paper we
    extend our study and confront QPO models with various NS equations of
    state (EoS). We start with simplified calculations assuming Kerr
    background geometry and then present results of detailed calculations
    considering the influence of NS quadrupole moment (related to
    rotationally induced NS oblateness) assuming Hartle-Thorne spacetimes.
    We show that the application of concrete EoS together with a particular
    QPO model yields a specific mass-angular-momentum relation. However, we
    demonstrate that the degeneracy in mass and angular momentum can be
    removed when the NS spin frequency inferred from the X-ray burst
    observations is considered. We inspect a large set of EoS and discuss
    their compatibility with the considered QPO models. We conclude that
    when the NS spin frequency in 4U 1636-53 is close to 580Hz we can
    exclude 51 from 90 of the considered combinations of EoS and QPO models.
    We also discuss additional restrictions that may exclude even more
    combinations. Namely, there are 13 EOS compatible with the observed twin
    peak QPOs and the relativistic precession model. However, when
    considering the low frequency QPOs and Lense-Thirring precession, only 5
    EOS are compatible with the model.

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

    http://adsabs.harvard.edu/abs/2016arXiv161106087T

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