The Emergence of a Lanthanide-rich Kilonova Following the Merger of Two Neutron Stars

N. R. Tanvir, A. J. Levan, C. González-Fernández, O. Korobkin, I. Mandel, S. Rosswog, J. Hjorth, P. D’Avanzo, A. S. Fruchter, C. L. Fryer, T. Kangas, B. Milvang-Jensen, S. Rosetti, D. Steeghs, R. T. Wollaeger, Zach Cano, C. M. Copperwheat, S. Covino, V. D’Elia, A. de Ugarte PostigoP. A. Evans, W. P. Even, S. Fairhurst, R. Figuera Jaimes, C. J. Fontes, Y. I. Fujii, J. P. U. Fynbo, B. P. Gompertz, J. Greiner, G. Hodosan, M. J. Irwin, Pall Jakobsson, U. G. Jørgensen, D. A. Kann, J. D. Lyman, D. Malesani, R. G. McMahon, A. Melandri, P. T. O’Brien, J. P. Osborne, E. Palazzi, D. A. Perley, E. Pian, S. Piranomonte, M. Rabus, E. Rol, A. Rowlinson, S. Schulze, P. Sutton, C. C. Thöne, K. Ulaczyk, D. Watson, K. Wiersema, R. A. M. J. Wijers

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289 Citations (Scopus)


We report the discovery and monitoring of the near-infrared counterpart (AT2017gfo) of a binary neutron-star merger event detected as a gravitational wave source by Advanced Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo (GW170817) and as a short gamma-ray burst by Fermi Gamma-ray Burst Monitor (GBM) and Integral SPI-ACS (GRB 170817A). The evolution of the transient light is consistent with predictions for the behavior of a "kilonova/macronova" powered by the radioactive decay of massive neutron-rich nuclides created via r-process nucleosynthesis in the neutron-star ejecta. In particular, evidence for this scenario is found from broad features seen in Hubble Space Telescope infrared spectroscopy, similar to those predicted for lanthanide-dominated ejecta, and the much slower evolution in the near-infrared ${K}_{{\rm{s}}}$-band compared to the optical. This indicates that the late-time light is dominated by high-opacity lanthanide-rich ejecta, suggesting nucleosynthesis to the third r-process peak (atomic masses $A\approx 195$). This discovery confirms that neutron-star mergers produce kilo-/macronovae and that they are at least a major—if not the dominant—site of rapid neutron capture nucleosynthesis in the universe.
Original languageEnglish
Pages (from-to)L27
JournalThe Astrophysical Journal Letters
Issue number2
Publication statusPublished - 16 Oct 2017

Other keywords

  • Gravitational waves
  • Nuclear reactions
  • Nucleosynthesis, abundances
  • Stars: neutron
  • Hubblessjónaukinn
  • Stjörnufræði
  • Stjarneðlisfræði


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