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
Fryer, C. L.; Berger, E.; Benoit-Lévy, A.; Bechtol, K.; Smith, N.; Smith, M.; Nichol, R. C.; D'Andrea, C. B.; Rest, A.; Finley, D. A.; Foley, R. J.; Kessler, R.; Marriner, J.; Zenteno, A.; Abbott, T. M. C.; Allam, S.; Annis, J.; Bertin, E.; Burke, D. L.; Carnero Rosell, A.; Carrasco Kind, M.; Castander, F. J.; Crocce, M.; Cunha, C. E.; da Costa, L. N.; Davis, C.; Desai, S.; Diehl, H. T.; Eifler, T. F.; Flaugher, B.; Fosalba, P.; García-Bellido, J.; Gaztanaga, E.; Gerdes, D. W.; Goldstein, D. A.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Johnson, M. W. G.; Kuehn, K.; Li, T. S.; Lima, M.; Maia, M. A. G.; Marshall, J. L.; Martini, P.; Menanteau, F.; Miller, C. J.; Miquel, R.; Ogando, R. L. C.; Plazas, A. A.; Romer, A. K.; Rykoff, E. S.; Sako, M.; Sanchez, E.; Scarpine, V.; Schindler, R.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Walker, A. R.; Carlin, J. L.; Balbinot, E.; Mohr, J. J.; Chornock, R.; Zhang, Y.; Palmese, A.; Jeltema, T.; Buckley-Geer, E.; Evrard, A. E.; Lahav, O.; March, M.; Roodman, A.; Thomas, D.; Durret, F.; Weller, J.; Muñoz, R. R.; Dietrich, J. P.; Banerji, M.; Brout, D.; Drlica-Wagner, A.; Fernandez, E.; Giannantonio, T.; Jain, B.; Johnson, M. D.; Krause, E.; Lin, H.; Muir, J.; Secco, L. F.; Troxel, M. A.; Vikram, V.; Wechsler, R. H.; Yanny, B.; Zuntz, J.; Fong, W.; Vivas, A. K.; Nicholl, M.; Eftekhari, T.; Metzger, B. D.; Tucker, D. L.; Lopes, P. A. A.; Quataert, E.; Matheson, T.; Wester, W.; DePoy, D. L.; Gill, M. S. S.; Kent, S.; Kron, R.; McMahon, R. G.; Neilsen, E.; Thomas, R. C.; Brown, D. A.; Farr, B.; Margutti, R.; Drout, M. R.; Capozzi, D.; Alexander, K. D.; Blanchard, P. K.; Schlegel, D. J.; Williams, P. K. G.; Medina, G. E.; Kasen, D.; Roe, N.; Scolnic, D. M.; Villar, V. A.; Cowperthwaite, P. S.; Doctor, Z.; Chen, H. -Y.; Frieman, J. A.; Holz, D. E.; Herner, K.; Sauseda, M.; Guillochon, J.; Butler, R. E.; Neilsen, E. H., Jr.; Cook, E. R.; Lourenço, A. C. C.; Nuropatkin, N.
United States, Spain, United Kingdom, France, Brazil, Chile, India, Germany, Australia
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≈ 4.5× {10}14 cm (corresponding to an expansion velocity of v≈ 0.3c), and a bolometric luminosity of {L}{bol}≈ 5× {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.