The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. II. UV, Optical, and Near-infrared Light Curves and Comparison to Kilonova Models
© 2017. The American Astronomical Society. All rights reserved.. 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 ≈ 4.5 × 1014cm (corresponding to an expansion velocity of v ≈ 0.3c), and a bolometric luminosity of Lbol ≈ 5 × 1041 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 Mblueej 0.1 M⊙ and vblueej ≈ 0.3c, and the "red" component has and Mredej ≈ 0.04 M⊙ and vredej ≈ 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.
Cowperthwaite, PS; Berger, E; Villar, VA; Metzger, BD; Nicholl, M; Chornock, R; Blanchard, PK; Fong, W; Margutti, R; Soares-Santos, M; Alexander, KD; Allam, S; Annis, J; Brout, D; Brown, DA; Butler, RE; Chen, HY; Diehl, HT; Doctor, Z; Drout, MR; Eftekhari, T; Farr, B; Finley, DA; Foley, RJ; Frieman, JA; Fryer, CL; García-Bellido, J; Gill, MSS; Guillochon, J; Herner, K; Holz, DE; Kasen, D; Kessler, R; Marriner, J; Matheson, T; Neilsen, EH; Quataert, E; Palmese, A; Rest, A; Sako, M; Scolnic, DM; Smith, N; Tucker, DL; Williams, PKG; Balbinot, E; Carlin, JL; Cook, ER; Durret, F; Li, TS; Lopes, PAA; Lourenço, ACC; Marshall, JL; Medina, GE; Muir, J; Muñoz, RR; Sauseda, M; Schlegel, DJ; Secco, LF; Vivas, AK; Wester, W; Zenteno, A; Zhang, Y; Abbott, TMC; Banerji, M; Bechtol, K; Benoit-Lévy, A; Bertin, E; Buckley-Geer, E; Burke, DL; Capozzi, D; Carnero Rosell, A; Carrasco Kind, M; Castander, FJ; Crocce, M; Cunha, CE; D'Andrea, CB; Costa, LND; Davis, C; Depoy, DL; Desai, S; Dietrich, JP; Drlica-Wagner, A; Eifler, TF; Evrard, AE; Fernandez, E; Flaugher, B; Fosalba, P; Gaztanaga, E; Gerdes, DW; Giannantonio, T; Goldstein, DA; Gruen, D; Gruendl, RA; Gutierrez, G; Honscheid, K; Jain, B; James, DJ; Jeltema, T; Johnson, MWG; Johnson, MD
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