The Complete Ultraviolet, Optical, and Near-Infrared Light Curves of the Kilonova Associated with the Binary Neutron Star Merger GW170817: Homogenized Data Set, Analytic Models, and Physical Implications

V. Ashley Villar, James Guillochon, Edo Berger, Brian D. Metzger, Philip S. Cowperthwaite, Matt Nicholl, Kate D. Alexander, Peter K. Blanchard, Ryan Chornock, Tarraneh Eftekhari, Wen-fai Fong, Raffaella Margutti, Peter K. G. Williams

Published 2017-10-31Version 1

We present the first effort to aggregate, homogenize, and uniformly model the complete ultraviolet, optical, and near-infrared dataset for the electromagnetic counterpart of the binary neutron star merger GW170817. By assembling all of the available data we are able to identify and mitigate systematic offsets between individual datasets, and to identify clear outlying measurements, with the resulting pruned and homogenized dataset offering an opportunity to expand the study of the kilonova. The homogenized dataset includes 625 individual flux measurements, spanning 0.45 to 29.4 days post-merger, and thus has greater constraining power for physical models than any single dataset. We test a number of semi-analytical models and find that the data are well modeled with a three-component kilonova model: a "blue" lanthanide-poor component with M~0.016 Msol and v~0.27c; an intermediate opacity "purple" component with M~0.04 Msol and v~0.14c; and a "red" lanthanide-rich component with M~0.009 Msol and v~0.08c. We further explore the possibility of ejecta asymmetry and its impact on the estimated parameters. From the inferred parameters we draw conclusions about the physical mechanisms responsible for the various ejecta components, the properties of the neutron stars, and, combined with an up-to-date merger rate, the implications for r-process enrichment via this channel. To facilitate future studies of this keystone event we make the homogenized dataset and our modeling code public.