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Wijnands R, Van Der Klis M, Homan J, et al. Quasi-periodic X-ray brightness fluctuations in an accreting millisecond pulsar. Nature. 2003;424(6944):44-7doi: 10.1038/nature01754.
Wijnands, R., Van Der Klis, M., Homan, J., Chakrabarty, D., Markwardt, C. B., & Morgan, E. H. (2003). Quasi-periodic X-ray brightness fluctuations in an accreting millisecond pulsar. Nature, 424(6944), 44-7. https://doi.org/10.1038/nature01754
Wijnands, R, et al. "Quasi-periodic X-ray brightness fluctuations in an accreting millisecond pulsar." Nature vol. 424,6944 (2003): 44-7. doi: https://doi.org/10.1038/nature01754
Wijnands R, Van Der Klis M, Homan J, Chakrabarty D, Markwardt CB, Morgan EH. Quasi-periodic X-ray brightness fluctuations in an accreting millisecond pulsar. Nature. 2003 Jul 03;424(6944):44-7. doi: 10.1038/nature01754. PMID: 12840752.
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Nature. 2003 Jul 03;424(6944):44-7. doi: 10.1038/nature01754.

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

Nature

R Wijnands, M Van Der Klis, J Homan, D Chakrabarty, C B Markwardt, E H Morgan

Affiliations

  1. School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK. [email protected]

PMID: 12840752 DOI: 10.1038/nature01754

Abstract

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 supra-nuclear-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. 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, 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.

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