Swift and NuSTAR observations of GW170817: detection of a blue kilonova

Funding for the Swift mission in the UK is provided by the UK Space Agency. SRO gratefully acknowledges the support of the Leverhulme Trust Early Career Fellowship (SRO). The Swift team at the MOC at Penn State acknowledges support from NASA contract NAS5-00136. The Italian Swift team acknowledge support from ASI-INAF grant I/004/11/3. SR has been supported by the Swedish Research Council (VR) under grant number 2016- 03657_3, by the Swedish National Space Board under grant number Dnr. 107/16 and by the research environment grant “Gravitational Radiation and Electromagnetic Astrophysical Transients (GREAT)” funded by the Swedish Research council (VR) under Dnr 2016- 06012. This research used resources provided by the Los Alamos National Laboratory Institutional Computing Program, which is supported by the U.S. Department of Energy National Nuclear Security Administration under Contract No. DE-AC52-06NA25396. VLT data were obtained under ESO program number 099.D-0668. NuSTAR acknowledges funding from NASA Contract No. NNG08FD60C. A.J.L. and N.R.T. acknowledge funding from the European Research Council under the European Union’s Horizon 2020 programme, grant number 725246. Researchers at Los Alamos National Laboratory were supported by the National Nuclear Security Administration of the US Department of Energy under contract number DEAC52-06NA25396. SWKE is supported by a Science and Technology Facilities Council studentship. The observations are archived at http://www.swift.ac.uk for Swift and https://heasarc.gsfc.nasa.gov/docs/nustar/nustar_archive.html for NuSTAR, under the observation IDs given in Table S2. Reduced photometry and surveyed areas are tabulated in the supplementary material. The boxfit on November 24, 2017 http://science.sciencemag.org/ Downloaded from First release: 16 October 2017 www.sciencemag.org (Page numbers not final at time of first release) 8 software is available at http://cosmo.nyu.edu/afterglowlibrary/boxfit201