• Cowperthwaite, P. S.
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• Berger, E.
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• Villar, V. A.
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• Metzger, B. D.
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• Nicholl, M.
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• Chornock, R.
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• Blanchard, P. K.
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• Fong, W.
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• Margutti, R.
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• Soares-Santos, M.
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• Alexander, K. D.
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• Allam, S.
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• Annis, J.
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• Brout, D.
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• Brown, D. A.
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• Butler, R. E.
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• Chen, H.-Y.
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• Diehl, H. T.
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• Doctor, Z.
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• Drout, M. R.
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• Eftekhari, T.
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• Farr, B.
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• Finley, D. A.
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• Foley, R. J.
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• Frieman, J. A.
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• Fryer, C. L.
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• García-Bellido, J.
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• Gill, M. S. S.
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• Guillochon, J.
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• Herner, K.
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• Holz, D. E.
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• Kasen, D.
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• Kessler, R.
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• Marriner, J.
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• Matheson, T.
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• Neilsen, E. H., Jr.
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• Quataert, E.
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• Palmese, A.
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• Rest, A.
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• Sako, M.
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• Scolnic, D. M.
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• Smith, N.
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• Tucker, D. L.
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• Williams, P. K. G.
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• Balbinot, E.
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• Carlin, J. L.
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• Cook, E. R.
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• Durret, F.
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• Li, T. S.
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• Lopes, P. A. A.
• and 94 more

Abstract

We present UV, optical, and near-infrared (NIR) photometry of the first electromagnetic counterpart to a gravitational wave source from Advanced Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo, the binary neutron star merger GW170817. Our data set extends from the discovery of the optical counterpart at 0.47-18.5 days post-merger, and includes observations with the Dark Energy Camera (DECam), Gemini-South/FLAMINGOS-2 (GS/F2), and the Hubble Space Telescope (HST). The spectral energy distribution (SED) inferred from this photometry at 0.6 days is well described by a blackbody model with T≈ 8300 K, a radius of R≈ ×ばつ {10}¹⁴ cm (corresponding to an expansion velocity of v≈ 0.3c), and a bolometric luminosity of {L}_{bol}≈ ×ばつ {10}⁴¹ erg s^-1. At 1.5 days we find a multi-component SED across the optical and NIR, and subsequently we observe rapid fading in the UV and blue optical bands and significant reddening of the optical/NIR colors. Modeling the entire data set, we find that models with heating from radioactive decay of ⁵⁶Ni, or those with only a single component of opacity from r-process elements, fail to capture the rapid optical decline and red optical/NIR colors. Instead, models with two components consistent with lanthanide-poor and lanthanide-rich ejecta provide a good fit to the data; the resulting "blue" component has {M}_{ej}^{blue}≈ 0.01 {M}_⊙ and {v}_{ej}^{blue}≈ 0.3 {{c}}, and the "red" component has {M}_{ej}^{red}≈ 0.04 {M}_⊙ and {v}_{ej}^{red}≈ 0.1 {{c}}. These ejecta masses are broadly consistent with the estimated r-process production rate required to explain the Milky Way r-process abundances, providing the first evidence that binary neutron star (BNS) mergers can be a dominant site of r-process enrichment.