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:

An ultraluminous X-ray source powered by an accreting neutron star

Nature volume 514, pages 202–204 (2014)Cite this article

Subjects

Abstract

The majority of ultraluminous X-ray sources are point sources that are spatially offset from the nuclei of nearby galaxies and whose X-ray luminosities exceed the theoretical maximum for spherical infall (the Eddington limit) onto stellar-mass black holes1,2. Their X-ray luminosities in the 0.5–10 kiloelectronvolt energy band range from 1039 to 1041 ergs per second3. Because higher masses imply less extreme ratios of the luminosity to the isotropic Eddington limit, theoretical models have focused on black hole rather than neutron star systems1,2. The most challenging sources to explain are those at the luminous end of the range (more than 1040 ergs per second), which require black hole masses of 50–100 times the solar value or significant departures from the standard thin disk accretion that powers bright Galactic X-ray binaries, or both. Here we report broadband X-ray observations of the nuclear region of the galaxy M82 that reveal pulsations with an average period of 1.37 seconds and a 2.5-day sinusoidal modulation. The pulsations result from the rotation of a magnetized neutron star, and the modulation arises from its binary orbit. The pulsed flux alone corresponds to an X-ray luminosity in the 3–30 kiloelectronvolt range of 4.9 × 1039 ergs per second. The pulsating source is spatially coincident with a variable source4 that can reach an X-ray luminosity in the 0.3–10 kiloelectronvolt range of 1.8 × 1040 ergs per second1. This association implies a luminosity of about 100 times the Eddington limit for a 1.4-solar-mass object, or more than ten times brighter than any known accreting pulsar. This implies that neutron stars may not be rare in the ultraluminous X-ray population, and it challenges physical models for the accretion of matter onto magnetized compact objects.

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 X-ray light curve and pulsations from the region containing NuSTAR J095551+6940.8.
Figure 2: The spin-up behaviour of NuSTAR J095551+6940.8.
Figure 3: The counterpart of NuSTAR J095551+6940.8.

Similar content being viewed by others

References

  1. Roberts, T. P. X-ray observations of ultraluminous X-ray sources. Astrophys. Space Sci. 311, 203–212 (2007)

    Article  ADS  Google Scholar 

  2. Liu, J.-F., Bregman, J. N., Bai, Y., Justham, S. & Crowther, P. Puzzling accretion onto a black hole in the ultraluminous X-ray source M 101 ULX-1. Nature 503, 500–503 (2013)

    Article  CAS  ADS  Google Scholar 

  3. Feng, H. & Soria, R. Ultraluminous X-ray sources in the Chandra and XMM-Newton era. New Astron. Rev. 55, 166–183 (2011)

    Article  ADS  Google Scholar 

  4. Feng, H., Rao, F. & Kaaret, P. Discovery of millihertz X-ray oscillations in a transient ultraluminous X-ray source in M82. Astrophys. J. 710, L137–L141 (2010)

    Article  ADS  Google Scholar 

  5. Skinner, G. K. et al. Discovery of 69 ms periodic X-ray pulsations in A0538–66. Nature 297, 568–570 (1982)

    Article  ADS  Google Scholar 

  6. Lucke, R., Yentis, D., Friedman, H., Fritz, G. & Shulman, S. Discovery of X-ray pulsations in SMC X-1. Astrophys. J. 206, L25–L28 (1976)

    Article  ADS  Google Scholar 

  7. Kouveliotou, C. et al. A new type of transient high-energy source in the direction of the Galactic Centre. Nature 379, 799–801 (1996)

    Article  CAS  ADS  Google Scholar 

  8. Basko, M. M. & Sunyaev, R. A. The limiting luminosity of accreting neutron stars with magnetic fields. Mon. Not. R. Astron. Soc. 175, 395–417 (1976)

    Article  ADS  Google Scholar 

  9. Gnedin, Y. N. & Sunyaev, R. A. The beaming of radiation from an accreting magnetic neutron star and the X-ray pulsars. Astron. Astrophys. 25, 233–239 (1973)

    CAS  ADS  Google Scholar 

  10. Basko, M. M. & Sunyaev, R. A. Radiative transfer in a strong magnetic field and accreting X-ray pulsars. Astron. Astrophys. 42, 311–321 (1975)

    ADS  Google Scholar 

  11. Harrison, F. A. et al. The Nuclear Spectroscopic Telescope Array (NuSTAR) high-energy X-ray mission. Astrophys. J. 770, 103–122 (2013)

    Article  ADS  Google Scholar 

  12. Kaaret, P. et al. Chandra High-Resolution Camera observations of the luminous X-ray source in the starburst galaxy M82. Mon. Not. R. Astron. Soc. 321, L29–L32 (2001)

    Article  CAS  ADS  Google Scholar 

  13. Kaaret, P., Simet, M. G. & Lang, C. C. A 62 day X-ray periodicity and an X-ray flare from the ultraluminous X-ray source in M82. Astrophys. J. 646, 174–183 (2006)

    Article  CAS  ADS  Google Scholar 

  14. Kong, A. K. H., Yang, Y. J., Hsieh, P. Y., Mak, D. S. Y. & Pun, C. S. J. The ultraluminous X-ray sources near the center of M82. Astrophys. J. 671, 349–357 (2007)

    Article  CAS  ADS  Google Scholar 

  15. Ransom, S. M. New Search Techniques for Binary Pulsars. PhD thesis, Harvard Univ. (2001)

  16. Bildsten, L. et al. Observations of accreting pulsars. Astrophys. J. Suppl. Ser. 113, 367–408 (1997)

    Article  ADS  Google Scholar 

  17. Canuto, V., Lodenquai, J. & Ruderman, M. Thomson scattering in a strong magnetic field. Phys. Rev. D 3, 2303–2308 (1971)

    Article  ADS  Google Scholar 

  18. Pringle, J. E. & Rees, M. J. Accretion disc models for compact X-ray sources. Astron. Astrophys. 21, 1–9 (1972)

    ADS  Google Scholar 

  19. Ghosh, P. & Lamb, F. K. Accretion by rotating magnetic neutron stars. III — Accretion torques and period changes in pulsating X-ray sources. Astrophys. J. 234, 296–316 (1979)

    Article  ADS  Google Scholar 

  20. Weisskopf, M. C. et al. An overview of the performance and scientific results from the Chandra X-ray observatory. Publ. Astron. Soc. Pacif. 114, 1–24 (2002)

    Article  ADS  Google Scholar 

  21. Goobar, A. et al. The rise of SN 2014J in the nearby galaxy M82. Astrophys. J. 784, L12 (2014)

    Article  ADS  Google Scholar 

  22. Davis, J. E. Event pileup in charge-coupled devices. Astrophys. J. 562, 575–582 (2001)

    Article  ADS  Google Scholar 

  23. Evans, P. A. et al. Methods and results of an automatic analysis of a complete sample of Swift-XRT observations of GRBs. Mon. Not. R. Astron. Soc. 397, 1177–1201 (2009)

    Article  CAS  ADS  Google Scholar 

  24. Houck, J. C. & Denicola, L. A. ISIS: an Interactive Spectral Interpretation System for high resolution X-ray spectroscopy. Astron. Data Analysis Softw. Syst. 216, 591–594 (2000)

    ADS  Google Scholar 

  25. Blandford, R. & Teukolsky, S. A. Arrival-time analysis for a pulsar in a binary system. Astrophys. J. 205, 580–591 (1976)

    Article  ADS  Google Scholar 

  26. Edwards, R. T., Hobbs, G. B. & Manchester, R. N. TEMPO2, a new pulsar timing package — II. The timing model and precision estimates. Mon. Not. R. Astron. Soc. 372, 1549–1574 (2006)

    Article  ADS  Google Scholar 

  27. Scargle, J. D. Studies in astronomical time series analysis. II — Statistical aspects of spectral analysis of unevenly spaced data. Astrophys. J. 263, 835–853 (1982)

    Article  ADS  Google Scholar 

  28. Cash, W. Parameter estimation in astronomy through application of the likelihood ratio. Astrophys. J. 228, 939–947 (1979)

    Article  ADS  Google Scholar 

  29. Arnaud, K. A. XSPEC: the first ten years. Astron. Data Analysis Softw. Syst. 101, 17–20 (1996)

    ADS  Google Scholar 

  30. Mitsuda, K. et al. Energy spectra of low-mass binary X-ray sources observed from TENMA. Astron. Soc. Jpn 36, 741–759 (1984)

    CAS  ADS  Google Scholar 

  31. Ranalli, P., Comastri, A., Origlia, L. & Maiolino, R. A deep X-ray observation of M82 with XMM-Newton. Mon. Not. R. Astron. Soc. 386, 1464–1480 (2008)

    Article  CAS  ADS  Google Scholar 

  32. Mewe, R., Gronenschild, E. H. B. M. & van den Oord, G. H. J. Calculated X-radiation from optically thin plasmas. V. Astron. Astrophys. Suppl. Ser. 62, 197–254 (1985)

    CAS  ADS  Google Scholar 

  33. Titarchuk, L. Generalized Comptonization models and application to the recent high-energy observations. Astrophys. J. 434, 570–586 (1994)

    Article  ADS  Google Scholar 

  34. Kalberla, P. M. W. et al. The Leiden/Argentine/Bonn (LAB) survey of Galactic HI. Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections. Astron. Astrophys. 440, 775–782 (2005)

    Article  CAS  ADS  Google Scholar 

Download references

Acknowledgements

This work was supported by NASA (grant no. NNG08FD60C), and made use of data from the Nuclear Spectroscopic Telescope Array (NuSTAR) mission, a project led by Caltech, managed by the Jet Propulsion Laboratory and funded by NASA. We thank the NuSTAR operations, software and calibration teams for support with execution and analysis of these observations. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. M.B. thanks the Centre National d’Études Spatiales (CNES) and the Centre National de la Recherche Scientifique (CNRS) for support. Line plots were done using Veusz software by J. Sanders.

Author information

Authors and Affiliations

  1. Université de Toulouse, UPS-OMP, Institut de Recherche en Astrophysique et Planétologie, 9, Avenue du Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France,

    M. Bachetti, D. Barret & N. A. Webb

  2. CNRS, Institut de Recherche en Astrophysique et Planétologie, 9, Avenue du Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France,

    M. Bachetti, D. Barret & N. A. Webb

  3. Cahill Center for Astrophysics, 1216 East California Boulevard, California Institute of Technology, Pasadena, 91125, California, USA

    F. A. Harrison, D. J. Walton, B. W. Grefenstette, F. Fürst, S. R. Kulkarni, V. Rana & S. P. Tendulkar

  4. MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, 02139, Massachusetts, USA

    D. Chakrabarty

  5. Physics Department, Columbia University, 538 West 120th Street, New York, New York 10027, USA,

    A. Beloborodov

  6. Space Sciences Laboratory, University of California, Berkeley, 94720, California, USA

    S. E. Boggs & J. Tomsick

  7. DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby, Denmark,

    F. E. Christensen

  8. Lawrence Livermore National Laboratory, Livermore, 94550, California, USA

    W. W. Craig

  9. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK,

    A. C. Fabian

  10. Columbia Astrophysics Laboratory, Columbia University, New York, 10027, New York, USA

    C. J. Hailey

  11. NASA Goddard Space Flight Center, Greenbelt, 20771, Maryland, USA

    A. Hornschemeier & W. W. Zhang

  12. Department of Physics, McGill University, Montreal, Quebec H3A 2T8, Canada,

    V. Kaspi

  13. Department of Physics, Texas Tech University, Lubbock, 79409, Texas, USA

    T. Maccarone

  14. Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, Michigan 48109-1042, USA,

    J. M. Miller

  15. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, 91109, California, USA

    D. Stern

Authors
  1. M. Bachetti
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. F. A. Harrison
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. D. J. Walton
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. B. W. Grefenstette
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. D. Chakrabarty
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. F. Fürst
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. D. Barret
    View author publications

    You can also search for this author in PubMed Google Scholar

  8. A. Beloborodov
    View author publications

    You can also search for this author in PubMed Google Scholar

  9. S. E. Boggs
    View author publications

    You can also search for this author in PubMed Google Scholar

  10. F. E. Christensen
    View author publications

    You can also search for this author in PubMed Google Scholar

  11. W. W. Craig
    View author publications

    You can also search for this author in PubMed Google Scholar

  12. A. C. Fabian
    View author publications

    You can also search for this author in PubMed Google Scholar

  13. C. J. Hailey
    View author publications

    You can also search for this author in PubMed Google Scholar

  14. A. Hornschemeier
    View author publications

    You can also search for this author in PubMed Google Scholar

  15. V. Kaspi
    View author publications

    You can also search for this author in PubMed Google Scholar

  16. S. R. Kulkarni
    View author publications

    You can also search for this author in PubMed Google Scholar

  17. T. Maccarone
    View author publications

    You can also search for this author in PubMed Google Scholar

  18. J. M. Miller
    View author publications

    You can also search for this author in PubMed Google Scholar

  19. V. Rana
    View author publications

    You can also search for this author in PubMed Google Scholar

  20. D. Stern
    View author publications

    You can also search for this author in PubMed Google Scholar

  21. S. P. Tendulkar
    View author publications

    You can also search for this author in PubMed Google Scholar

  22. J. Tomsick
    View author publications

    You can also search for this author in PubMed Google Scholar

  23. N. A. Webb
    View author publications

    You can also search for this author in PubMed Google Scholar

  24. W. W. Zhang
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

M.B., reduction and timing analysis of the NuSTAR observations, interpretation of results, manuscript preparation; F.A.H., interpretation of results, manuscript preparation; D.J.W., NuSTAR and Chandra spectroscopy, point source analysis; B.W.G., NuSTAR image analysis; D.C., accretion torque analysis, interpretation; F.F., verification of timing analysis, interpretation; D.B., A.B., A.C.F., A.H., V.M.K., T.M., J.T., interpretation of results and manuscript review; S.B., F.C., W.W.C., C.J.H., D.S., S.P.T., N.W., W.W.Z., manuscript review.

Corresponding authors

Correspondence to M. Bachetti or F. A. Harrison.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Extended data figures and tables

Extended Data Figure 1 X-ray sources identified by Chandra in the central region of M82.

a, Chandra image of the central region of M82 from the observation taken coincident with NuSTAR ObsID 006. The yellow circle shows the 70″ radius region used to extract NuSTAR fluxes. Within this region, 24 discrete X-ray point sources are identified, including X-1 and X-2. b, Expanded view of the crowded central region of a. Yellow crosses indicate the locations of identified point sources. We have used, where possible, the numbering from ref. 13 (sources up to no. 15). After this we assign our own numerical identification (note that sources 4 and 10 from ref. 13 are not detected in this observation).

Extended Data Figure 2 Swift imaging of the region containing M82 X-1 and M82 X-2.

a, b, In greyscale are images obtained via Swift automated processing over the 5–10 keV band for all of the observations during early February (a; 2014 February 04 through 2014 February 11) and mid-March (b; 2014 March 7 through 2014 March 11). The early February observations have 68.5 ks of exposure (mostly because of the increased cadence of observations due to the Swift monitoring of SN 2014J), while the mid-March snapshot has 1.8 ks of exposure. The images are 1.5 arcmin on a side and have been smoothed with a 2-pixel (4 arcsecond) Gaussian kernel (circle at lower left). The location of X-1 and X-2 are shown by the crosses in both panels. The late-time observation clearly shows a reduction in the flux from X-1 and that the flux is dominated by X-2.

Extended Data Table 1 List of NuSTAR observations used in this analysis
Full size table
Extended Data Table 2 Best-fit orbital parameters
Full size table
Extended Data Table 3 Best fit period and period derivatives for individual NuSTAR observations
Full size table
Extended Data Table 4 3–10 keV flux contributions for bright sources near the nucleus of M82
Full size table

Related audio

PowerPoint slides

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Bachetti, M., Harrison, F., Walton, D. et al. An ultraluminous X-ray source powered by an accreting neutron star. Nature 514, 202–204 (2014). https://doi.org/10.1038/nature13791

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature13791

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