2017/10/16 by P. A. Evans, S. B. Cenko, J. A. Kennea +56 · 3 citations
Physics and Astronomy · #astro-ph.HE
paper · pdf · doi:10.1126/science.aap9580
Science, in press; 56 pages, 12 figures
arxiv created 2017/10/16 · arxiv updated 2017/10/17
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 (NuSTAR) of the EM counterpart of the binary neutron star merger GW170817. The bright, rapidly fading ultraviolet 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 ultra-relativistic, highly collimated ejecta (a gamma-ray burst afterglow).