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

Here, 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 thus 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.
Authors:
ORCiD logo [1] ;  [2] ;  [3] ; ORCiD logo [4] ;  [5] ;  [6] ; ORCiD logo [7] ;  [8] ;  [9] ; ORCiD logo [4] ;  [9] ; ORCiD logo [7] ;  [1] ;  [2] ;  [4] ; ORCiD logo [10] ;  [11] ; ORCiD logo [8] ;  [12] ;  [13] more »;  [1] ; ORCiD logo [4] ; ORCiD logo [14] ;  [15] ;  [4] ; ORCiD logo [16] ;  [7] ;  [2] ;  [17] ;  [10] ; ORCiD logo [3] ;  [18] ;  [7] ; ORCiD logo [10] ;  [2] ; ORCiD logo [7] ; ORCiD logo [3] ;  [8] ;  [1] ;  [1] ;  [19] ; ORCiD logo [11] ; ORCiD logo [19] ;  [20] ; ORCiD logo [21] ;  [22] ;  [23] ;  [24] ;  [14] ;  [10] ;  [2] ; ORCiD logo [7] ; ORCiD logo [1] ;  [25] « less
  1. Univ. of Leicester (United Kingdom)
  2. Univ. of Warwick, Coventry (United Kingdom)
  3. Univ. of Cambridge (United Kingdom)
  4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  5. Univ. of Birmingham (United Kingdom)
  6. Stockholm Univ. (Sweden)
  7. Univ. of Copenhagen (Denmark). The Niels Bohr Inst.
  8. National Inst. for Astrophysics (INAF), Merate (Italy)
  9. Space Telescope Science Inst., Baltimore, MD (United States)
  10. Astrophysical Inst. of Andalusia, Granada (Spain)
  11. Liverpool John Moores Univ. (United Kingdom)
  12. Space Science Data Center, Rome (Italy); National Inst. for Astrophysics (INAF), Cantone (Italy)
  13. Univ. of Copenhagen (Denmark). The Niels Bohr Inst.; Astrophysical Inst. of Andalusia, Granada (Spain)
  14. Cardiff Univ. (United Kingdom)
  15. Univ. of St. Andrews, Scotland (United Kingdom)
  16. Univ. of Copenhagen (Denmark). The Niels Bohr Inst.; Nagoya Univ. (Japan)
  17. Max Planck Inst. for Extraterrestrial Physics, Garching (Germany)
  18. Univ. of Iceland, Reykjavik (Iceland)
  19. National Inst. for Astrophysics (INAF), Bologna (Italy)
  20. National Inst. for Astrophysics (INAF), Catone (Italy)
  21. Pontifical Catholic Univ. of Chile, Santiago (Chile)
  22. Monash Univ., Melbourne, VIC (Australia)
  23. Univ. of Amsterdam (Netherlands); Netherlands Inst. for Radio Astronomy, Dwingeloo (Netherlands)
  24. Weizmann Inst. of Science, Rehovot (Israel)
  25. Univ. of Amsterdam (Netherlands)
Publication Date:
Report Number(s):
LA-UR-17-29025
Journal ID: ISSN 2041-8213; TRN: US1702928
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal. Letters
Additional Journal Information:
Journal Volume: 848; Journal Issue: 2; Journal ID: ISSN 2041-8213
Publisher:
Institute of Physics (IOP)
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; kilonova, neutron star, merger, r-process, nucleosynthesis, lanthanides
OSTI Identifier:
1407907