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

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.

12 pages, 9 figures, 3 tables, accepted for publication in The Astrophysical Journal

References in corpus (17)

• Shapiro delay measurement of a two solar mass neutron star
• A Massive Pulsar in a Compact Relativistic Binary
• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• Relativistic Mean-Field Hadronic Models under Nuclear Matter Constraints
• Constraints on the high-density nuclear equation of state from the phenomenology of compact stars and heavy-ion collisions
• Modern compact star observations and the quark matter equation of state
• Using Neutron Star Observations to Determine Crust Thicknesses, Moments of Inertia, and Tidal Deformabilities
• Cold uniform matter and neutron stars in the quark-mesons-coupling model
• The coherence of kHz quasi-periodic oscillations in the X-rays from accreting neutron stars
• Tidal effects on small bodies by massive black holes
• On the maximum amplitude and coherence of the kilohertz quasi-periodic oscillations in low-mass X-ray binaries
• RossiXTE monitoring of 4U 1636-53: I. Long-term evolution and kHz Quasi-Periodic Oscillations
• On mass-constraints implied by the relativistic precession model of twin-peak quasi-periodic oscillations in Circinus X-1
• Mass-angular-momentum relations implied by models of twin peak quasi-periodic oscillations
• Gravitational excitation of high frequency QPOs
• Epicyclic frequencies for rotating strange quark stars: the importance of stellar oblateness
• Appearance of innermost stable circular orbits of accretion discs around rotating neutron stars

Cited by in corpus (5)

• Timescale of twin-peak quasi-periodic oscillations and mass of accreting neutron stars
• Dragged surfaces. On the accretion tori in the ergoregion
• Simple analytic formula relating the mass and spin of accreting compact objects to their rapid X-ray variability
• On one-parametric formula relating the frequencies of twin-peak quasi-periodic oscillations
• Lense-Thirring precession of neutron-star accretion flows: Relativistic versus classical precession