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A two-solar-mass neutron star measured using Shapiro delay

Nature volume 467, pages 1081–1083 (2010)Cite this article

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Abstract

Neutron stars are composed of the densest form of matter known to exist in our Universe, the composition and properties of which are still theoretically uncertain. Measurements of the masses or radii of these objects can strongly constrain the neutron star matter equation of state and rule out theoretical models of their composition1,2. The observed range of neutron star masses, however, has hitherto been too narrow to rule out many predictions of ‘exotic’ non-nucleonic components3,4,5,6. The Shapiro delay is a general-relativistic increase in light travel time through the curved space-time near a massive body7. For highly inclined (nearly edge-on) binary millisecond radio pulsar systems, this effect allows us to infer the masses of both the neutron star and its binary companion to high precision8,9. Here we present radio timing observations of the binary millisecond pulsar J1614-223010,11 that show a strong Shapiro delay signature. We calculate the pulsar mass to be (1.97 ± 0.04)M⊙, which rules out almost all currently proposed2,3,4,5 hyperon or boson condensate equations of state (M⊙, solar mass). Quark matter can support a star this massive only if the quarks are strongly interacting and are therefore not ‘free’ quarks12.

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Figure 1: Shapiro delay measurement for PSR J1614-2230.
Figure 2: Results of the MCMC error analysis.
Figure 3: Neutron star mass–radius diagram.

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References

  1. Lattimer, J. M. & Prakash, M. The physics of neutron stars. Science 304, 536–542 (2004)

    Article  ADS  CAS  Google Scholar 

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

    Article  ADS  CAS  Google Scholar 

  3. Glendenning, N. K. & Schaffner-Bielich, J. Kaon condensation and dynamical nucleons in neutron stars. Phys. Rev. Lett. 81, 4564–4567 (1998)

    Article  ADS  CAS  Google Scholar 

  4. Lackey, B. D., Nayyar, M. & Owen, B. J. Observational constraints on hyperons in neutron stars. Phys. Rev. D 73, 024021 (2006)

    Article  ADS  CAS  Google Scholar 

  5. Schulze, H., Polls, A., Ramos, A. & Vidaña, I. Maximum mass of neutron stars. Phys. Rev. C 73, 058801 (2006)

    Article  ADS  CAS  Google Scholar 

  6. Kurkela, A., Romatschke, P. & Vuorinen, A. Cold quark matter. Phys. Rev. D 81, 105021 (2010)

    Article  ADS  CAS  Google Scholar 

  7. Shapiro, I. I. Fourth test of general relativity. Phys. Rev. Lett. 13, 789–791 (1964)

    Article  ADS  MathSciNet  Google Scholar 

  8. Jacoby, B. A., Hotan, A., Bailes, M., Ord, S. & Kulkarni, S. R. The mass of a millisecond pulsar. Astrophys. J. 629, L113–L116 (2005)

    Article  ADS  Google Scholar 

  9. Verbiest, J. P. W. et al. Precision timing of PSR J0437–4715: an accurate pulsar distance, a high pulsar mass, and a limit on the variation of Newton’s gravitational constant. Astrophys. J. 679, 675–680 (2008)

    Article  ADS  CAS  Google Scholar 

  10. Hessels, J. et al. in Binary Radio Pulsars (eds Rasio, F. A. & Stairs, I. H.) 395 (ASP Conf. Ser. 328, Astronomical Society of the Pacific, 2005)

    Google Scholar 

  11. Crawford, F. et al. A survey of 56 midlatitude EGRET error boxes for radio pulsars. Astrophys. J. 652, 1499–1507 (2006)

    Article  ADS  CAS  Google Scholar 

  12. Özel, F., Psaltis, D., Ransom, S., Demorest, P. & Alford, M. The massive pulsar PSR J1614−2230: linking quantum chromodynamics, gamma-ray bursts, and gravitational wave astronomy. Astrophys. J. (in the press)

  13. Hobbs, G. B., Edwards, R. T. & Manchester, R. N. TEMPO2, a new pulsar-timing package - I. An overview. Mon. Not. R. Astron. Soc. 369, 655–672 (2006)

    Article  ADS  Google Scholar 

  14. Damour, T. & Deruelle, N. General relativistic celestial mechanics of binary systems. II. The post-Newtonian timing formula. Ann. Inst. Henri Poincaré Phys. Théor. 44, 263–292 (1986)

    MathSciNet  MATH  Google Scholar 

  15. Freire, P. C. C. & Wex, N. The orthometric parameterisation of the Shapiro delay and an improved test of general relativity with binary pulsars. Mon. Not. R. Astron. Soc (in the press)

  16. Iben, I., Jr & Tutukov, A. V. On the evolution of close binaries with components of initial mass between 3 solar masses and 12 solar masses. Astrophys. J Suppl. Ser. 58, 661–710 (1985)

    Article  ADS  CAS  Google Scholar 

  17. Özel, F. Soft equations of state for neutron-star matter ruled out by EXO 0748 - 676. Nature 441, 1115–1117 (2006)

    Article  ADS  CAS  Google Scholar 

  18. Ransom, S. M. et al. Twenty-one millisecond pulsars in Terzan 5 using the Green Bank Telescope. Science 307, 892–896 (2005)

    Article  ADS  CAS  Google Scholar 

  19. Freire, P. C. C. et al. Eight new millisecond pulsars in NGC 6440 and NGC 6441. Astrophys. J. 675, 670–682 (2008)

    Article  ADS  CAS  Google Scholar 

  20. Freire, P. C. C., Wolszczan, A., van den Berg, M. & Hessels, J. W. T. A massive neutron star in the globular cluster M5. Astrophys. J. 679, 1433–1442 (2008)

    Article  ADS  Google Scholar 

  21. Alford, M. et al. Astrophysics: quark matter in compact stars? Nature 445, E7–E8 (2007)

    Article  CAS  Google Scholar 

  22. Lattimer, J. M. & Prakash, M. Ultimate energy density of observable cold baryonic matter. Phys. Rev. Lett. 94, 111101 (2005)

    Article  ADS  CAS  Google Scholar 

  23. Podsiadlowski, P., Rappaport, S. & Pfahl, E. D. Evolutionary sequences for low- and intermediate-mass X-ray binaries. Astrophys. J. 565, 1107–1133 (2002)

    Article  ADS  CAS  Google Scholar 

  24. Podsiadlowski, P. & Rappaport, S. Cygnus X-2: the descendant of an intermediate-mass X-Ray binary. Astrophys. J. 529, 946–951 (2000)

    Article  ADS  Google Scholar 

  25. Hotan, A. W., van Straten, W. & Manchester, R. N. PSRCHIVE and PSRFITS: an open approach to radio pulsar data storage and analysis. Publ. Astron. Soc. Aust. 21, 302–309 (2004)

    Article  ADS  Google Scholar 

  26. Cordes, J. M. & Lazio, T. J. W. NE2001.I. A new model for the Galactic distribution of free electrons and its fluctuations. Preprint at 〈http://arxiv.org/abs/astro-ph/0207156〉 (2002)

  27. Lattimer, J. M. & Prakash, M. Neutron star structure and the equation of state. Astrophys. J. 550, 426–442 (2001)

    Article  ADS  Google Scholar 

  28. Champion, D. J. et al. An eccentric binary millisecond pulsar in the Galactic plane. Science 320, 1309–1312 (2008)

    Article  ADS  CAS  Google Scholar 

  29. Berti, E., White, F., Maniopoulou, A. & Bruni, M. Rotating neutron stars: an invariant comparison of approximate and numerical space-time models. Mon. Not. R. Astron. Soc. 358, 923–938 (2005)

    Article  ADS  Google Scholar 

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Acknowledgements

P.B.D. is a Jansky Fellow of the National Radio Astronomy Observatory. J.W.T.H. is a Veni Fellow of The Netherlands Organisation for Scientific Research. We thank J. Lattimer for providing the EOS data plotted in Fig. 3, and P. Freire, F. Özel and D. Psaltis for discussions. The National Radio Astronomy Observatory is a facility of the US National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

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Authors and Affiliations

  1. National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, Virginia 22093, USA,

    P. B. Demorest & S. M. Ransom

  2. Astronomy Department, University of Virginia, Charlottesville, 22094-4325, Virginia, USA

    T. Pennucci

  3. Eureka Scientific, Inc., Oakland, 94602, California, USA

    M. S. E. Roberts

  4. Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo, The Netherlands,

    J. W. T. Hessels

  5. Astronomical Institute “Anton Pannekoek”, University of Amsterdam, 1098 SJ Amsterdam, The Netherlands

    J. W. T. Hessels

Authors
  1. P. B. Demorest
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  2. T. Pennucci
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  3. S. M. Ransom
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  4. M. S. E. Roberts
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  5. J. W. T. Hessels
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Contributions

All authors contributed to collecting data, discussed the results and edited the manuscript. In addition, P.B.D. developed the MCMC code, reduced and analysed data, and wrote the manuscript. T.P. wrote the observing proposal and created Fig. 3. J.W.T.H. originally discovered the pulsar. M.S.E.R. initiated the survey that found the pulsar. S.M.R. initiated the high-precision timing proposal.

Corresponding author

Correspondence to P. B. Demorest.

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The authors declare no competing financial interests.

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Demorest, P., Pennucci, T., Ransom, S. et al. A two-solar-mass neutron star measured using Shapiro delay. Nature 467, 1081–1083 (2010). https://doi.org/10.1038/nature09466

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