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

We present the first effort to aggregate, homogenize, and uniformly model the combined ultraviolet, optical, and nearinfrared data set for the electromagnetic counterpart of the binary neutron star merger GW170817. By assembling all of the available data from 18 different papers and 46 different instruments, we are able to identify and mitigate systematic offsets between individual data sets and to identify clear outlying measurements, with the resulting pruned and adjusted data set offering an opportunity to expand the study of the kilonova. The unified data set includes 647 individual flux measurements, spanning 0.45-29.4 days post-merger, and thus has greater constraining power for physical models than any single data set. We test a number of semi-analytical models and find that the data are well modeled with a threecomponent kilonova model: a blue lanthanide-poor component (k = 0.5 cm(2) g(-1)) with M-ej approximate to 0.020M circle dot and v(ej) approximate to 0.27c; an intermediate opacity purple component (k = 3 cm(2) g(-1)) with M-ej approximate to 0.047M circle dot and v(ej) approximate to 0.15c; and a red lanthanide-rich component (k = 10 cm(2) g(-1)) withM(ej) approximate to 0.011M. and v(ej) approximate to 0.14c. 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 unified data set and our modeling code public.