Kilohertz quasi-periodic oscillations in low-mass X-ray binaries

Abstract

In early 1996 a series of discoveries begun with NASA's Rossi X-ray Timing Explorer of a new, up to then unknown astrophysical phenomenon. It turned out that accreting low magnetic-field neutron stars show quasi-periodic oscillations in their X-ray flux at rates of up to more than a kilohertz. These kHz QPO, now reported from eleven different systems, are among the fastest phenomena in the sky and can provide us with new information about the fundamental properties of neutron stars and help testing general relativity in the strong-field regime. If, for example, their frequencies can be identified with the Keplerian frequencies of matter in orbit around a 1.4 Solar-mass neutron star, then the radius of the star would have to be less than 15 km, which directly constrains the equation of state of bulk nuclear-density matter, and for an only slightly tighter orbit or slightly more massive neutron star the orbital radius would equal the Schwarzschild-geometry general-relativistic marginally stable orbit (12.5 km for a 1.4 Solar mass object). So far all models that have been put forward for explaining the new phenomenon have encountered problems. In this paper I review the relatively simple and highly suggestive phenomenology as it has emerged from the data up to now, and discuss some of the proposed models.

To be published in the Proceedings of the Wise Observatory 25th Anniversary Symposium "Astronomical Time Series", Tel Aviv, January 1997

References in corpus (9)

• Black Hole Spin in X-Ray Binaries: Observational Consequences
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• RXTE Discovery of Coherent Millisecond Pulsations during an X-ray Burst from KS 1731-260
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• KiloHertz Quasi-Periodic Oscillations in GX 17+2
• Discovery of Two Simultaneous Kilohertz Quasi-Periodic Oscillations in KS 1731-260
• Strong-field general relativity and quasi-periodic oscillations in x-ray binaries
• Energy Spectra and High Frequency Oscillations in 4U 0614+091
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• Measurement of neutron star parameters: a review of methods for low-mass X-ray binaries
• Implementation of the frequency-modulated sideband search method for gravitational waves from low mass X-ray binaries
• Alive but Barely Kicking: News from 3+ years of Swift and XMM-Newton X-ray Monitoring of Quasi-Periodic Eruptions from eRO-QPE1
• A Systematic Spectral-Timing Analysis of Kilohertz Quasi-Periodic Oscillations in the Rossi X-ray Timing Explorer Archive
• ASTROSAT: Some Key Science Prospects
• The slowest spinning X-ray pulsar in an extragalactic globular cluster
• XMM-Newton discovery of mHz quasi-periodic oscillations in the high mass X-ray binary IGRJ19140+0951
• Detailed Analysis of the Pulsations During and After Bursts from the Bursting Pulsar (GRO J1744-28)
• Spectral-Timing Analysis of the Lower kHz QPO in the Low-Mass X-ray Binary Aquila X-1
• Discovery of Quasi Periodic Oscillations in the persistent X-ray emission of Accreting Binary X-ray Pulsar LMC X-4
• Modeling the upper kHz QPOs of 4U 1728-34 with X-ray reverberation
• Timing of accreting neutron stars with future X-ray instruments: towards new constraints on dense matter equation of state
• A Search for Aperiodic Millisecond Variability in Cygnus X-1
• Dynamics of magnetoviscous warped discs around compact objects