Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

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

Nature volume 424, pages 44–47 (2003)Cite this article

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 flows1,2,3. 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 frequency4,5,6,7,8,9,10, 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.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Figure 1: The power-density spectra obtained for SAX J1808.4–3658 during its 2002 outburst.
Figure 2: The power-density spectrum obtained for SAX J1808.4–3658 using the combined data from 18–19 October and 22–26 October.

Similar content being viewed by others

References

  1. Svartsman, V. F. Halos around black holes. Sov. Astron 15, 377–384 (1971)

    ADS  Google Scholar 

  2. Van der Klis, M. et al. Intensity dependent quasi-periodic oscillations in the X-ray flux of GX 5-1. Nature 316, 225–230 (1985)

    Article  ADS  CAS  Google Scholar 

  3. Van der Klis, M. Millisecond oscillations in X-ray binaries. Annu. Rev. Astron. Astrophys. 38, 717–760 (2000)

    Article  ADS  Google Scholar 

  4. Alpar, M. A. & Shaham, J. Is GX. 5-1. a millisecond pulsar? Nature 316, 239–241 (1985)

    Article  ADS  Google Scholar 

  5. Lamb, F. K., Shibazaki, N., Alpar, M. A. & Shaham, J. Quasi-periodic oscillations in bright galactic-bulge X-ray sources. Nature 317, 681–687 (1985)

    Article  ADS  Google Scholar 

  6. Miller, C. M., Lamb, F. K. & Psaltis, D. Sonic-point model of kilohertz quasi-periodic brightness oscillations in low-mass X-ray binaries. Astrophys. J. 508, 791–830 (1998)

    Article  ADS  Google Scholar 

  7. Stella, L. & Vietri, M. KHz quasi-periodic oscillations in low-mass X-ray binaries as probes of general relativity in the strong-field regime. Phys. Rev. Lett. 82, 17–20 (1999)

    Article  ADS  CAS  Google Scholar 

  8. Titarchuk, L., Lapidus, I. & Muslimov, A. Mechanisms for high-frequency quasi-periodic oscillations in neutron stars and black hole binaries. Astrophys. J. 449, 315–328 (1998)

    Article  ADS  Google Scholar 

  9. Kluźniak, W. & Abramowicz, M. A. The physics of kHz QPOs—strong gravity's coupled anharmonic oscillators. Astrophys. J. Lett. (submitted); preprint at 〈http://xxx.lanl.gov/astro-ph/0105057〉 (2001)

  10. Psaltis, D. & Norman, C. On the origin of quasi-periodic oscillations and broad-band noise in accreting neutron stars and black holes. Astrophys. J. (submitted); preprint at 〈http://xxx.lanl.gov/astro-ph/0001391〉 (2000)

  11. Strohmayer, T. & Bildsten, L. New views of thermonuclear bursts. In Compact Stellar X-ray Sources (eds Lewin, W. H. G. & van der Klis, M.) (Cambridge Univ. Press, in the press); preprint at 〈http://xxx.lanl.gov/astro-ph/0301544〉 (2003)

    Google Scholar 

  12. Strohmayer, T. E. et al. Millisecond X-ray variability from an accreting neutron star system. Astrophys. J. 469, L9–L12 (1996)

    Article  ADS  CAS  Google Scholar 

  13. Cui, W. On the disappearance of kilohertz quasi-periodic oscillations at high mass accretion rate in low-mass X-ray binaries. Astrophys. J. 534, L31–L34 (2000)

    Article  ADS  CAS  Google Scholar 

  14. Campana, S. Kilohertz quasi-periodic oscillations in low-mass X-ray binary sources and their relation to the neutron star magnetic field. Astrophys. J. 534, L79–L82 (2000)

    Article  ADS  CAS  Google Scholar 

  15. Muno, M. P., Özel, F. & Chakrabarty, D. The amplitude evolution and harmonic content of millisecond oscillations in thermonuclear X-ray bursts. Astrophys. J. 581, 550–561 (2002)

    Article  ADS  Google Scholar 

  16. Van der Klis, M., Wijnands, R. A. D., Horne, K. & Chen, W. Kilohertz quasi-periodic oscillation peak separation is not constant in Scorpius X-1. Astrophys. J. 481, L97–L101 (1997)

    Article  ADS  Google Scholar 

  17. Méndez, M. et al. Kilohertz quasi-periodic oscillation peak separation is not constant in the atoll source 4U 1608-52. Astrophys. J. 505, L23–L26 (1998)

    Article  ADS  Google Scholar 

  18. Méndez, M., van der Klis, M. & van Paradijs, J. Difference frequency of kilohertz QPOs not equal to half the burst oscillation frequency in 4U 1636-53. Astrophys. J. 506, L117–L119 (1998)

    Article  ADS  Google Scholar 

  19. Jonker, P. G., Méndez, M. & van der Klis, M. Kilohertz quasi-periodic oscillations difference frequency exceeds inferred spin frequency in 4U 1636-53. Mon. Not. R. Astron. Soc. 336, L1–L5 (2002)

    Article  ADS  Google Scholar 

  20. Lamb, F. K. & Miller, M. C. Changing frequency separation of kilohertz quasi-periodic oscillations in the sonic-point beat-frequency model. Astrophys. J. 554, 1210–1215 (2001)

    Article  ADS  Google Scholar 

  21. Wijnands, R. & van der Klis, M. A millisecond pulsar in an X-ray binary system. Nature 394, 344–346 (1998)

    Article  ADS  CAS  Google Scholar 

  22. Markwardt, C. B., Miller, J. M. & Wijnands, R. SAX J1808.4-3658. IAU Circ. No. 7993 (2002)

  23. Chakrabarty, D. et al. Nuclear-powered millisecond pulsars and the maximum spin frequency of neutron stars. Nature (this issue)

  24. Shibazaki, N. & Lamb, F. K. Power spectra of quasi-periodic oscillations in luminous X-ray stars. Astrophys. J. 318, 767–785 (1987)

    Article  ADS  CAS  Google Scholar 

  25. Psaltis, D. Models of quasi-periodic variability in neutron stars and black holes. Adv. Space Res. 555, 786–800 (2001)

    Google Scholar 

  26. Stella, L. in X-ray Astronomy: Stellar Endpoints, AGN, and the Diffuse X-ray Backgroud (eds White, N. E., Malaguti, G. & Palumbo, G. G. C.) 365–375 (AIP Conference Proceedings Vol. 599, Melville, New York, 2001)

    Google Scholar 

  27. van der Klis, M. in XEUS–Studying the Evolution of the Hot Universe (eds Hasinger, G., Boller, Th. & Parmar, A.) 354–362 (MPE Report 281, 2002)

    Google Scholar 

  28. Abramowicz, M. A., Karas, V., Kluźniak, W., Lee, W. H. & Rebusco, P. Non-linear resonance in nearly geodesic motion in low-mass X-ray binaries. Publ. Astron. Soc. Jpn 55, 467–471 (2003)

    Article  ADS  CAS  Google Scholar 

  29. Jonker, P. G., Méndez, M. & van der Klis, M. Discovery of a new, third kilohertz quasi-periodic oscillations in 4U 1608-52, 4U 1728-34, and 4U 1636-53: Sidebands to the lower kilohertz quasi-periodic oscillation? Astrophys. J. 540, L29–L32 (2000)

    Article  ADS  Google Scholar 

  30. Stella, L. & Vietri, M. Lense-Thirring precession and quasi-periodic oscillations in low-mass X-ray binaries. Astrophys. J. 492, L59–L62 (1998)

    Article  ADS  Google Scholar 

Download references

Acknowledgements

We thank J. Swank and E. Smith for their efforts in scheduling our RXTE observations of SAX J1808.4–3658, and D. Psaltis for discussions. M.v.d.K. was supported by NWO.

Author information

Authors and Affiliations

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

    R. Wijnands

  2. Astronomical Institute ‘Anton Pannekoek’, University of Amsterdam,

    M. van der Klis

  3. Centre for High-Energy Astrophysics, Kruislaan 403, 1098 SJ, Amsterdam, The Netherlands

    M. van der Klis

  4. INAF-Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807, Merate LC, Italy

    J. Homan

  5. Center for Space Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA

    D. Chakrabarty & E.H. Morgan

  6. Laboratory for High Energy Astrophysics, NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771, USA

    C.B. Markwardt

Authors
  1. R. Wijnands
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. M. van der Klis
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. J. Homan
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. D. Chakrabarty
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. C.B. Markwardt
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. E.H. Morgan
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to R. Wijnands.

Ethics declarations

Competing interests

The authors declare that they have no competing financial interests.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Wijnands, R., van der Klis, M., Homan, J. et al. Quasi-periodic X-ray brightness fluctuations in an accreting millisecond pulsar. Nature 424, 44–47 (2003). https://doi.org/10.1038/nature01754

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature01754

This article is cited by

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing