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Science. 2017 Dec 22;358(6370):1565-1570. doi: 10.1126/science.aap9580. Epub 2017 Oct 16.

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

Author information

1
University of Leicester, X-ray and Observational Astronomy Research Group, Leicester Institute for Space and Earth Observation, Department of Physics and Astronomy, University Road, Leicester LE1 7RH, UK. pae9@leicester.ac.uk.
2
Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.
3
Joint Space-Science Institute, University of Maryland, College Park, MD 20742, USA.
4
Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA.
5
University College London, Mullard Space Science Laboratory, Holmbury St. Mary, Dorking RH5 6NT, UK.
6
Center for Theoretical Astrophysics, Los Alamos National Laboratory, Los Alamos, NM 87545 USA.
7
Cahill Center for Astronomy and Astrophysics, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA.
8
The Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel.
9
Center for Computational Astrophysics, Simons Foundation, 162 5th Avenue, New York, NY 10010, USA.
10
Center for Research and Exploration in Space Science and Technology (CRESST) and NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.
11
Department of Physics, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA.
12
Istituto Nazionale di Astrofisica (INAF)-Osservatorio Astronomico di Brera, Via Bianchi 46, I-23807 Merate, Italy.
13
Department of Physics, University of Warwick, Coventry CV4 7AL, UK.
14
Department of Physics and Astronomy, University of Maryland, College Park, MD 20742-4111, USA.
15
University of Leicester, X-ray and Observational Astronomy Research Group, Leicester Institute for Space and Earth Observation, Department of Physics and Astronomy, University Road, Leicester LE1 7RH, UK.
16
INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica Palermo, via Ugo La Malfa 153, I-90146, Palermo, Italy.
17
INAF-Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monteporzio Catone, Italy.
18
Space Science Data Center-Agenzia Spaziale Italiana (ASI), I-00133 Roma, Italy.
19
Department of Astronomy and Space Sciences, University of Istanbul, Beyzt 34119, Istanbul, Turkey.
20
Department of Physical Sciences, Southern Utah University, Cedar City, UT 84720, USA.
21
Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802, USA.
22
Kinard Lab of Physics, Department of Physics and Astronomy, Clemson University, Clemson, SC 29634-0978, USA.
23
Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, CA 91125, USA.
24
Universities Space Research Association, 7178 Columbia Gateway Drive, Columbia, MD 21046, USA.
25
National Science Foundation, 2415 Eisenhower Avenue, Alexandria, VA 22314, USA.
26
Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark.
27
Los Alamos National Laboratory, B244, Los Alamos, NM 87545, USA.
28
The Oskar Klein Centre, Department of Astronomy, AlbaNova, Stockholm University, SE-106 91 Stockholm, Sweden.
29
Department of Physics and Mathematics, Aoyama Gakuin University, Sagamihara, Kanagawa, 252-5258, Japan.

Abstract

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 counterpart 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 γ-ray burst afterglow).

PMID:
29038371
DOI:
10.1126/science.aap9580

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