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A neutron star with a carbon atmosphere in the Cassiopeia A supernova remnant

Nature volume 462, pages 7173 (05 November 2009) | Download Citation

Abstract

The surface of hot neutron stars is covered by a thin atmosphere. If there is accretion after neutron-star formation, the atmosphere could be composed of light elements (H or He); if no accretion takes place or if thermonuclear reactions occur after accretion, heavy elements (for example, Fe) are expected. Despite detailed searches, observations have been unable to confirm the atmospheric composition of isolated neutron stars1. Here we report an analysis of archival observations of the compact X-ray source in the centre of the Cassiopeia A supernova remnant. We show that a carbon atmosphere neutron star (with low magnetic field) produces a good fit to the spectrum. Our emission model, in contrast with others2,3,4, implies an emission size consistent with theoretical predictions for the radius of neutron stars. This result suggests that there is nuclear burning in the surface layers5,6 and also identifies the compact source as a very young (330-year-old) neutron star.

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References

  1. 1.

    , & in Proc. WE-Heraeus Seminar: Neutron Stars, Pulsars and Supernova Remnants (eds Becker, W., Lesch, H., & Trümper, J.) Vol. 270 273–286 (MPE Report 278, MPI, 2002)

  2. 2.

    , , , & The compact central object in Cassiopeia A: a neutron star with hot polar caps or a black hole? Astrophys. J. 531, L53–L56 (2000)

  3. 3.

    , , , & The central X-ray point source in Cassiopeia A. Astrophys. J. 548, 800–810 (2001)

  4. 4.

    & A dedicated Chandra ACIS observation of the central compact object in the Cassiopeia A supernova remnant. Astrophys. J. 703, 910–921 (2009)

  5. 5.

    Hydrogen and helium abundances in neutron-star atmospheres. Astrophys. Space Sci. 1, 372–387 (1968)

  6. 6.

    & Evolution of young neutron star envelopes. Astrophys. J. 605, 830–839 (2004)

  7. 7.

    , , & The three-dimensional structure of the Cassiopeia A supernova remnant. I. The spherical shell. Astrophys. J. 440, 706–721 (1995)

  8. 8.

    A probable Flamsteed observation of the Cassiopeia A supernova. J. Hist. Astron. 11, 1–9 (1980)

  9. 9.

    et al. The expansion asymmetry and age of the Cassiopeia A supernova remnant. Astrophys. J. 645, 283–292 (2006)

  10. 10.

    Cassiopeia A. IAU Circ. 7246, (1999)

  11. 11.

    , , , & Advanced CCD imaging spectrometer (ACIS) instrument on the Chandra X-ray Observatory. Proc. SPIE 4851, 28–44 (2003)

  12. 12.

    et al. A million second Chandra view of Cassiopeia A. Astrophys. J. 615, L117–L120 (2004)

  13. 13.

    , , & A hydrogen atmosphere spectral model applied to the neutron star X7 in the globular cluster 47 Tucanae. Astrophys. J. 644, 1090–1103 (2006)

  14. 14.

    & Neutron star observations: prognosis for equation of state constraints. Phys. Rep. 442, 109–165 (2007)

  15. 15.

    , , , & Is the compact source at the center of Cassiopeia A pulsed? Astrophys. J. 566, 1039–1044 (2002)

  16. 16.

    & Pulselike character of blackbody radiation from neutron stars. Astrophys. J. 271, 283–293 (1983)

  17. 17.

    & Neutron star cooling. Annu. Rev. Astron. Astrophys. 42, 169–210 (2004)

  18. 18.

    , & The cooling of compact stars. Nucl. Phys. A 777, 497–530 (2006)

  19. 19.

    et al. Thermal evolution of hyperon-mixed neutron stars. Astrophys. J. 691, 621–632 (2009)

  20. 20.

    , & The evolution and explosion of massive stars. Rev. Mod. Phys. 74, 1015–1071 (2002)

  21. 21.

    & Discovery of a 112 ms X-ray pulsar in Puppis A: further evidence of neutron stars weakly magnetized at birth. Astrophys. J. 695, L35–L39 (2009)

  22. 22.

    & Delayed switch-on of pulsars. Astrophys. J. 440, L77–L80 (1995)

  23. 23.

    , , & XMM-Newton observation of the galactic centre—evidence against the X-ray reflection nebulae model? Astron. Nachr. 324, 73–76 (2003)

  24. 24.

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

  25. 25.

    & Surface chemistry of stars. I. Diffusion of heavy ions in white dwarf envelopes. Astrophys. J. 235, 534–540 (1980)

  26. 26.

    The Opacity Project Team. The Opacity Project〉 (2009)

  27. 27.

    & Model atmospheres for low-field neutron stars. Astrophys. J. 461, 327–333 (1996)

  28. 28.

    , & Model neutron star atmospheres with low magnetic fields. Astron. Astrophys. 315, 141–152 (1996)

  29. 29.

    & Atmospheres and spectra of strongly magnetized neutron stars. Mon. Not. R. Astron. Soc. 327, 1081–1096 (2001)

  30. 30.

    & Modelling mid-Z element atmospheres for strongly magnetized neutron stars. Mon. Not. R. Astron. Soc. 377, 905–919 (2007)

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Acknowledgements

W.C.G.H. thanks N. Badnell, P. Chang, and D. Lai for discussions. W.C.G.H. appreciates the use of the computer facilities at the Kavli Institute for Particle Astrophysics and Cosmology. W.C.G.H. acknowledges support from the Science and Technology Facilities Council (STFC) in the United Kingdom. C.O.H. acknowledges support from the Natural Sciences and Engineering Research Council (NSERC) of Canada.

Author Contributions W.C.G.H. calculated the new models and wrote the manuscript. C.O.H. reduced the data, fitted the models to the data, and contributed to the manuscript.

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Affiliations

  1. School of Mathematics, University of Southampton, Southampton SO17 1BJ, UK

    • Wynn C. G. Ho
  2. Department of Physics, University of Alberta, Room 238 CEB, 11322-89 Avenue, Edmonton, AB T6G 2G7, Canada

    • Craig O. Heinke

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Correspondence to Wynn C. G. Ho or Craig O. Heinke.

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https://doi.org/10.1038/nature08525

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