Swift and NuSTAR observations of GW170817: detection of a blue kilonova
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).
Additional Information
© 2017 American Association for the Advancement of Science. Received 14 September 2017; accepted 4 October 2017; Published online 16 October 2017. We acknowledge the leadership and scientific vision of Neil Gehrels (1952–2017), former PI of Swift, without whom the work we present here would not have been possible. 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 DE-AC52-06NA25396. 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 software is available at http://cosmo.nyu.edu/afterglowlibrary/boxfit2011.html, SUPERNU at https://bitbucket.org/drrossum/supernu/wiki/Home, access to WINNET source code and input files will be granted upon request via: https://bitbucket.org/korobkin/winnet. The dynamical model ejecta are available at http://compact-merger.astro.su.se/downloads_fluid_trajectories.html (as run 12). The SUPERNU and BOXFIT input files are available in the supplementary materials.Attached Files
Accepted Version - 1710.05437.pdf
Supplemental Material - aap9580-Evans-SM.pdf
Supplemental Material - aap9580-Evans-SM_add_data.zip
Files
Additional details
- Eprint ID
- 82060
- Resolver ID
- CaltechAUTHORS:20171004-130639886
- United Kingdom Space Agency (UKSA)
- Leverhulme Trust
- NAS5-00136
- NASA
- I/004/11/3
- Agenzia Spaziale Italiana (ASI)
- 2016-03657_3
- Swedish Research Council
- Dnr. 107/16
- Swedish National Space Board
- Dnr 2016-06012
- Swedish Research Council
- DE-AC52-06NA25396
- Department of Energy (DOE)
- NNG08FD60C
- NASA
- 725246
- European Research Council (ERC)
- Science and Technology Facilities Council (STFC)
- Created
-
2017-10-16Created from EPrint's datestamp field
- Updated
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2021-11-15Created from EPrint's last_modified field
- Caltech groups
- NuSTAR, Space Radiation Laboratory, Astronomy Department