Quasi-periodic X-ray brightness fluctuations in an accreting millisecond pulsar

Article

关键词: OSCILLATION PEAK SEPARATION;    NEUTRON-STAR;    DIFFERENCE-FREQUENCY;    4U 1636-53;    BINARIES;    SYSTEM;    MODEL;    PRECESSION;    CONSTANT;    FIELD;   

DOI  :  10.1038/nature01754

来源: SCIE

【 摘 要 】

The relativistic plasma flows onto neutron stars that are accreting material from stellar companions can be used to probe strong-field gravity as well as the physical conditions in the supranuclear-density interiors of neutron stars. Plasma inhomogeneities orbiting a few kilometres above the stars are observable as X-ray brightness fluctuations on the millisecond dynamical timescale of the flows(1-3). Two frequencies in the kilohertz range dominate these fluctuations: the twin kilohertz quasi-periodic oscillations (kHz QPOs). Competing models for the origins of these oscillations (based on orbital motions) all predict that they should be related to the stellar spin frequency(4-10), but tests have been difficult because the spins were not unambiguously known. Here we report the detection of kHz QPOs from a pulsar whose spin frequency is known. Our measurements establish a clear link between kHz QPOs and stellar spin, but one not predicted by any current model. A new approach to understanding kHz QPOs is now required. We suggest that a resonance between the spin and general relativistic orbital and epicyclic frequencies could provide the observed relation between QPOs and spin.

【 授权许可】

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