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The unpolarized macronova associated with the gravitational wave event GW 170817

An Author Correction to this article was published on 30 October 2017

This article has been updated


The merger of two dense stellar remnants including at least one neutron star is predicted to produce gravitational waves (GWs) and short-duration gamma ray bursts1,2. In the process, neutron-rich material is ejected from the system and heavy elements are synthesized by r-process nucleosynthesis1,3. The radioactive decay of these heavy elements produces additional transient radiation termed kilonova or macronova4,5,6,7,8,9,10. We report the detection of linear optical polarization, P = (0.50 ± 0.07)%, 1.46 days after detection of the GWs from GW 170817—a double neutron star merger associated with an optical macronova counterpart and a short gamma ray burst11,12,13,14. The optical emission from a macronova is expected to be characterized by a blue, rapidly decaying component and a red, more slowly evolving component due to material rich in heavy elements—the lanthanides15. The polarization measurement was made when the macronova was still in its blue phase, during which there was an important contribution from a lanthanide-free outflow. The low degree of polarization is consistent with intrinsically unpolarized emission scattered by galactic dust, suggesting a symmetric geometry of the emitting region and low inclination of the merger system. Stringent upper limits to the polarization degree from 2.45–9.48 days post-burst are consistent with the lanthanides-rich macronova interpretation.

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Fig. 1: Q/U Stokes parameter plot for the optical transient and several field stars near to the transient.

Change history

  • 30 October 2017

    In the version of this Letter originally published, in the third paragraph of the text Kyutoku  et al. were not correctly cited and the sentence should have read: “As pointed out by Kyutoku at al.28, in the case of high optical depth to electron scattering (~1) and assuming spectral lines do not significantly depolarize the global emission, the linear polarization observed from the equatorial plane could be as high as a few per cent.” Also, in the Author contributions section, the final sentence should have read: “C.G.M. contributed to the writing of the paper.”


  1. Eichler, D., Livio, M., Piran, T. & Schramm, D. N. Nucleosynthesis, neutrino bursts and gamma-rays from coalescing neutron stars. Nature 340,126–128 (1989).

    ADS  Article  Google Scholar 

  2. Berger, E. Short-duration gamma-ray bursts. Annu. Rev. Astron. Astrophys. 52, 43–105 (2014).

    ADS  Article  Google Scholar 

  3. Rosswog, S. et al. Mass ejection in neutron star mergers. Astron. Astrophys. 341, 499–526 (1999).

    ADS  Google Scholar 

  4. Li, L.-X. & Paczyński, B. Transient events from neutron star mergers. Astrophys. J. 507, L59–L62 (1998).

    ADS  Article  Google Scholar 

  5. Rosswog, S. Mergers of neutron star-black hole binaries with small mass ratios: nucleosynthesis, gamma-ray bursts, and electromagnetic transients. Astrophys. J. 634, 1202–1213 (2005).

    ADS  Article  Google Scholar 

  6. Metzger, B. D. et al. Electromagnetic counterparts of compact object mergers powered by the radioactive decay of r-process nuclei. Mon. Not. R. Astron. Soc. 406, 2650–2662 (2010).

    ADS  Article  Google Scholar 

  7. Kasen, D., Badnell, N. R. & Barnes, J. Opacities and spectra of the r-process ejecta from neutron star mergers. Astrophys. J. 774, 25 (2013).

    ADS  Article  Google Scholar 

  8. Barnes, J. & Kasen, D. Effect of a high opacity on the light curves of radioactively powered transients from compact object mergers. Astrophys. J. 775, 18 (2013).

    ADS  Article  Google Scholar 

  9. Tanaka, M. & Hotokezaka, K. Radiative transfer simulations of neutron star merger ejecta. Astrophys. J. 775, 113 (2013).

    ADS  Article  Google Scholar 

  10. Baiotti, L. & Rezzolla, L. Binary neutron star mergers: a review of Einstein’s richest laboratory. Rep. Prog. Phys. 80, 096901 (2017).

    ADS  MathSciNet  Article  Google Scholar 

  11. Abbott, B. P. et al. (LIGO Scientific Collaboration and Virgo Collaboration) GW170817: Observation of gravitational waves from a binary neutron star inspiral. Phys. Rev. Lett. (2017).

  12. Savchenko, V. et al. INTEGRAL detection of the first prompt gamma-ray signal coincident with the gravitational event GW170817. Astrophys. J. Lett. (2017).

  13. Goldstein et al. An ordinary short gamma-ray burst with extraordinary implications: Fermi-GBM detection of GRB 170817A. Astrophys. J. Lett. (2017).

  14. Coulter, D. et al. Swope Supernova Survey 2017a (SSS17a), the optical counterpart to a gravitational wave source. Science (2017).

  15. Kasen, D., Fernàndez, R. & Metzger, B. D. Kilonova light curves from the disc wind outflows of compact object mergers. Mon. Not. R. Astron. Soc. 450, 1777–1786 (2015).

    ADS  Article  Google Scholar 

  16. Pian, E. et al. Spectroscopic identification of r-process nucleosynthesis in a double neutron star merger. Nature (2017).

  17. Tanvir, N. R. et al. A 'kilonova' associated with the short-duration γ-ray burst GRB 130603B. Nature 500, 547–549 (2013).

    ADS  Article  Google Scholar 

  18. Yang, B. et al. A possible macronova in the late afterglow of the ‘long-short’ burst GRB 060614. Nat. Commun. 6, 7323 (2015).

    Article  Google Scholar 

  19. Jin, Z.-P. et al. The light curve of the macronova associated with the long-short burst GRB 060614. Astrophys. J. 811, L22 (2015).

    ADS  Article  Google Scholar 

  20. Jin, Z.-P. et al. The macronova in GRB 050709 and the GRB–macronova connection. Nat. Commun. 7, 12898 (2016).

    ADS  Article  Google Scholar 

  21. Ghirlanda, G. et al. Short gamma-ray bursts at the dawn of the gravitational wave era. Astron. Astrophys. 594, A84 (2016).

    Article  Google Scholar 

  22. Jin, Z.-P. et al. Short GRBs with small opening angles: implications on local neutron star merger rate and GRB/GW association. Preprint at (2017).

  23. Mundell, C. G. et al. Highly polarized light from stable ordered magnetic fields in GRB 120308A. Nature 504, 119–121 (2013).

    ADS  Article  Google Scholar 

  24. Wiersema, K. et al. Circular polarization in the optical afterglow of GRB 121024A. Nature 509, 201–204 (2014).

    ADS  Article  Google Scholar 

  25. Goriely, S., Bauswein, A. & Janka, H.-T. r-process nucleosynthesis in dynamically ejected matter of neutron star mergers. Astrophys. J. 738, L32 (2011).

    ADS  Article  Google Scholar 

  26. Hotokezaka, K. et al. Remnant massive neutron stars of binary neutron star mergers: evolution process and gravitational waveform. Phys. Rev. D 88, 044026 (2013).

    ADS  Article  Google Scholar 

  27. Kiuchi, K., Cerdà-Duràn, P., Kyutoku, K., Sekiguchi, Y. & Shibata, M. Efficient magnetic- field amplification due to the Kelvin–Helmholtz instability in binary neutron star mergers. Phys. Rev. D 92, 124034 (2015).

    ADS  Article  Google Scholar 

  28. Kyutoku, K., Ioka, K., Okawa, H., Shibata, M. & Taniguchi, K. Dynamical mass ejection from black hole-neutron star binaries. Phys. Rev. D 92, 044028 (2015).

    ADS  Article  Google Scholar 

  29. Tanaka, M. et al. Radioactively powered emission from black hole-neutron star mergers. Astrophys. J. 780, 31 (2014).

    ADS  Article  Google Scholar 

  30. Granot, J., Panaitescu, A., Kumar, P. & Woosley, S. E. Off-axis afterglow emission from jetted gamma-ray bursts. Astrophys. J. 570, L61–L64 (2002).

    ADS  Article  Google Scholar 

  31. Aasi, J. et al. Characterization of the LIGO detectors during their sixth science run. Classical and Quantum Gravity 32, 074001 (2015).

    ADS  Article  Google Scholar 

  32. Acernese, F. et al. Advanced Virgo: a second-generation interferometric gravitational wave detector. Class. Quantum Grav. 32, 024001 (2015).

    ADS  Article  Google Scholar 

  33. Serkowski, K., Mathewson, D. S. & Ford, V. L. Wavelength dependence of interstellar polarization and ratio of total to selective extinction. Astrophys. J. 196, 261–290 (1975).

    ADS  Article  Google Scholar 

  34. Plaszczynski, S., Montier, L., Levrier, F. & Tristram, M. A novel estimator of the polarization amplitude from normally distributed Stokes parameters. Mon. Not. R. Astron. Soc. 439, 4048–4056 (2014).

    ADS  Article  Google Scholar 

  35. Wiersema, K. et al. Detailed optical and near-infrared polarimetry, spectroscopy and broad-band photometry of the afterglow of GRB 091018: polarization evolution. Mon. Not. R. Astron. Soc. 426, 2–22 (2012).

    ADS  Article  Google Scholar 

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This study was based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under European Southern Observatory programme 099.D-0116. We thank the European Southern Observatory—Paranal staff for carrying out excellent observations under difficult conditions during a hectic period. We also acknowledge partial funding from Agenzia Spaziale Italiana-Istituto Nazionale di Astrofisica grant I/004/11/3. K.W., A.B.H., R.L.C.S. and N.R.T. acknowledge funding from the Science and Technology Facilities Council. J.H. was supported by a VILLUM FONDEN Investigator grant (project number 16599). Y.Z.F. was supported by the National Natural Science Foundation of China under grant 11525313. C.G.M. acknowledges support from the UK Science and Technology Facilities Council. K.T. was supported by Japan Society for the Promotion of Science grant 15H05437 and a Japan Science and Technology Consortia grant. J.M. acknowledges the National Natural Science Foundation of China 11673062 and the Major Program of the Chinese Academy of Sciences(KJZD-EW-M06).

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All authors contributed to the work presented in this paper. S.C. and K.W. coordinated the data acquisition, analysed the data and wrote the paper. A.B.H., A.M., P.D., E.P. and N.T. contributed to the data analysis. Y.F. and K.T. contributed to the theoretical discussion. C.G.M. contributed to the writing of the paper.

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Correspondence to S. Covino.

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Covino, S., Wiersema, K., Fan, Y.Z. et al. The unpolarized macronova associated with the gravitational wave event GW 170817. Nat Astron 1, 791–794 (2017).

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