The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. IV. Detection of Near-infrared Signatures of r-process Nucleosynthesis with Gemini-South

Abstract We present a near-infrared spectral sequence of the electromagnetic counterpart to the binary neutron star merger GW170817 detected by Advanced Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo. Our data set comprises seven epochs of J + H spectra taken with FLAMINGOS-2 on Gemini-South between 1.5 and 10.5 days after the merger. In the initial epoch, the spectrum is dominated by a smooth blue continuum due to a high-velocity, lanthanide-poor blue kilonova component. Starting the following night, all of the subsequent spectra instead show features that are similar to those predicted in model spectra of material with a high concentration of lanthanides, including spectral peaks near 1.07…

• NS
  National Science Foundation

  Awards: 1518052, PHY-1707954, AST-1518052, DE-AC02-07CH11359, 1707954, 1411763, 1714498, DE-AC02-05CH11231, NAS 5-26555, AST-1714498
• UD
  U.S. Department of Energy

  Awards: -AC02-05CH11231, DE-AC02-07CH11359, Contract No. DE-AC02-05CH11231, 05CH11231, No. DE-AC02-05CH11231, AC02-07CH11359, AC02-05CH11231, DE-AC02, NAS 5-26555, DE-AC02-05CH11231, DE-SC0017616, DE AC02-05CH11231, DE-AC02-
• NA
  National Aeronautics and Space Administration

  Awards: NNX16AC22G, DE-AC02-05CH11231, NNX15AE50G, NAS 5-26555, 5-26555
• AP
  Alfred P. Sloan Foundation

  Award: DE-AC02-05CH11231
• GA
  Gordon and Betty Moore Foundation

  Award: GBMF5076
• ST
  Space Telescope Science Institute

  Awards: NAS 5-26555, 5-26555, 26555
• NR
  National Research Foundation
• DG
  Danmarks Grundforskningsfond
• MD
  Ministerio de Ciencia, Tecnología e Innovación Productiva
• MD
  Ministério da Ciência, Tecnologia e Inovação
• OO
  Office of Science

  Awards: AC02-05CH11231, -AC02-05CH11231, DE-AC02, DE-AC02-07CH11359, DE AC02-05CH11231, No. DE-AC02-05CH11231, Contract No. DE-AC02-05CH11231
• CN
  Comisión Nacional de Investigación Científica y Tecnológica
• HE
  High Energy Physics

  Award: DE-AC02-05CH11231
• NP
  Nuclear Physics

  Award: DE-AC02-05CH11231