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】
Free