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

P. A. Evans, S. B. Cenko, J. A. Kennea, S. W.K. Emery, N. P.M. Kuin, O. Korobkin, R. T. Wollaeger, C. L. Fryer, K. K. Madsen, F. A. Harrison, Y. Xu, E. Nakar, K. Hotokezaka, A. Lien, S. Campana, S. R. Oates, E. Troja, A. A. Breeveld, F. E. Marshall, S. D. BarthelmyA. P. Beardmore, D. N. Burrows, G. Cusumano, A. D’Aì, P. D’Avanzo, V. D’Elia, M. De Pasquale, W. P. Even, C. J. Fontes, K. Forster, J. Garcia, P. Giommi, B. Grefenstette, C. Gronwall, D. H. Hartmann, M. Heida, A. L. Hungerford, M. M. Kasliwal, H. A. Krimm, A. J. Levan, D. Malesani, A. Melandri, H. Miyasaka, J. A. Nousek, P. T. O’Brien, J. P. Osborne, C. Pagani, K. L. Page, D. M. Palmer, M. Perri, S. Pike, J. L. Racusin, S. Rosswog, M. H. Siegel, T. Sakamoto, B. Sbarufatti, G. Tagliaferri, N. R. Tanvir, A. Tohuvavohu

Research output: Contribution to journalArticlepeer-review

410 Scopus citations


With the first direct detection of merging black holes in 2015, the era of gravitational wave (GW) astrophysics began. A complete picture of compact object mergers, however, requires the detection of an electromagnetic (EM) counterpart. We report ultraviolet (UV) and x-ray observations by Swift and the Nuclear Spectroscopic Telescope Array of the EM counter part of the binary neutron star merger GW170817. The bright, rapidly fading UV emission indicates a high mass (≈0.03 solar masses) wind-driven outflow with moderate electron fraction (Ye ≈ 0.27). Combined with the x-ray limits, we favor an observer viewing angle of ≈30° away from the orbital rotation axis, which avoids both obscuration from the heaviest elements in the orbital plane and a direct view of any ultrarelativistic, highly collimated ejecta (a g-ray burst afterglow).

Original languageEnglish (US)
Pages (from-to)1565-1570
Number of pages6
Issue number6370
StatePublished - Dec 22 2017

All Science Journal Classification (ASJC) codes

  • General


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