Article open access publication

Early spectra of the gravitational wave source GW170817: Evolution of a neutron star merger

Science, American Association for the Advancement of Science (AAAS), ISSN 0036-8075

Volume 358, 6370, 2017

DOI:10.1126/science.aaq0186, Dimensions: pub.1092247865, PMID: 29038374,



  1. (1) University of Hawaii at Manoa, grid.410445.0
  2. (2) Carnegie Observatories, grid.432988.c
  3. (3) Las Campanas Observatory, grid.440392.8
  4. (4) Millennium Institute of Astrophysics, grid.450287.c
  5. (5) Diego Portales University, grid.412193.c
  6. (6) Lawrence Berkeley National Laboratory, grid.184769.5
  7. (7) University of California, Berkeley, grid.47840.3f
  8. (8) University of California, Santa Cruz, grid.205975.c
  9. (9) University of Copenhagen, grid.5254.6, KU
  10. (10) Space Telescope Science Institute, grid.419446.a
  11. (11) Johns Hopkins University, grid.21107.35
  12. (12) California Institute of Technology, grid.20861.3d
  13. (13) Massachusetts Institute of Technology, grid.116068.8
  14. (14) National Autonomous University of Mexico, grid.9486.3
  15. (15) National Research Council (NRC) Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada.
  16. (16) University of Victoria, grid.143640.4
  17. (17) University of Valparaíso, grid.412185.b
  18. (18) Texas A&M University, grid.264756.4
  19. (19) University of Notre Dame, grid.131063.6
  20. (20) University of Sydney, grid.1013.3


On 17 August 2017, Swope Supernova Survey 2017a (SSS17a) was discovered as the optical counterpart of the binary neutron star gravitational wave event GW170817. We report time-series spectroscopy of SSS17a from 11.75 hours until 8.5 days after the merger. Over the first hour of observations, the ejecta rapidly expanded and cooled. Applying blackbody fits to the spectra, we measured the photosphere cooling from [Formula: see text] to [Formula: see text] kelvin, and determined a photospheric velocity of roughly 30% of the speed of light. The spectra of SSS17a began displaying broad features after 1.46 days and evolved qualitatively over each subsequent day, with distinct blue (early-time) and red (late-time) components. The late-time component is consistent with theoretical models of r-process-enriched neutron star ejecta, whereas the blue component requires high-velocity, lanthanide-free material.

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Times Cited: 105

Field Citation Ratio (FCR): 39.42

Relative Citation ratio (RCR): 0.79

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