A kilonova as the electromagnetic counterpart to a gravitational-wave source

S J Smartt ¹, T-W Chen ², A Jerkstrand ³

¹Astrophysics Research Centre, School of Mathematics and Physics, Queens University Belfast, Belfast BT7 1NN, UK.
²Max-Planck-Institut für Extraterrestrische Physik, Giessenbach-Strasse 1, D-85748 Garching, Munich, Germany.
³Max-Planck Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, D-85748 Garching, Munich, Germany.
⁴LIGO Laboratory West Bridge, Room 257 California Institute of Technology, MC 100-36, Pasadena, California 91125, USA.
⁵School of Physics, O'Brien Centre for Science North, University College Dublin, Belfield, Dublin 4, Ireland.
⁶Department of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, UK.
⁷Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, Hawaii 96822, USA.
⁸Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark.
⁹Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100, Israel.
¹⁰Department of Physics, University of Warwick, Coventry CV4 7AL, UK.
¹¹Institute for Astronomy, SUPA (Scottish Universities Physics Alliance), University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK.
¹²Departamento de Ciencias Fisicas, Universidad Andres Bello, Avenida de Republica 252, Santiago, Chile.
¹³Millennium Institute of Astrophysics (MAS), Nuncio Monseñor Sótero Sanz 100, Providencia, Santiago, Chile.
¹⁴European Southern Observatory, Alonso de Córdova 3107, Casilla 19, Santiago, Chile.
¹⁵Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK.
¹⁶The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, 10691 Stockholm, Sweden.
¹⁷Instituto de Astrofísica and Centro de Astroingeniería, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile.
¹⁸Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, Colorado 80301, USA.
¹⁹Dipartimento di Fisica e Astronomia 'G. Galilei', Università di Padova, Vicolo dell'Osservatorio 3, 35122 Padova, Italy.
²⁰INAF - Osservatorio Astronomico di Brera, via E. Bianchi 46, 23807 Merate, Italy.
²¹INAF - Osservatorio Astronomico di Capodimonte, via Salita Moiariello 16, 80131 Napoli, Italy.
²²The Oskar Klein Centre, Department of Physics, Stockholm University, AlbaNova, 10691 Stockholm, Sweden.
²³SRON, Netherlands Institute for Space Research, Sorbonnelaan 2, NL-3584 CA Utrecht, The Netherlands.
²⁴Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, NL-6500 GL Nijmegen, The Netherlands.
²⁵Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía, E-18008 Granada, Spain.
²⁶European Southern Observatory, Karl-Schwarzschild Strasse 2, 85748 Garching bei München, Germany.
²⁷ICRANet-Pescara, Piazza della Repubblica 10, I-65122 Pescara, Italy.
²⁸IAP/CNRS and University Pierre et Marie Curie, Paris, France.
²⁹Unidad Mixta Internacional Franco-Chilena de Astronomía (CNRS UMI 3386), Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile.
³⁰Istituto Nazionale di Astrofisica, Viale del Parco Mellini 84, I-00136 Roma, Italy.
³¹Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching bei München, Germany.
³²Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen, Germany.
³³Institute of Cosmology and Gravitation, Dennis Sciama Building, University of Portsmouth, Burnaby Road, Portsmouth PO1 3FX, UK.
³⁴PITT PACC, Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
³⁵CENTRA, Instituto Superior Técnico - Universidade de Lisboa, Lisbon, Portugal.
³⁶Warsaw University Astronomical Observatory, Aleje Ujazdowskie 4, 00-478 Warszawa, Poland.
³⁷Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany.
³⁸Tuorla observatory, Department of Physics and Astronomy, University of Turku, Väisäläntie 20, FI-21500 Piikkiö, Finland.
³⁹Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhagi 5, 107 Reykjavík, Iceland.
⁴⁰Instituto de Física y Astronomía, Universidad de Valparaiso, Gran Bretaña 1111, Playa Ancha, Valparaíso 2360102, Chile.
⁴¹Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK.
⁴²Department of Physics, Lancaster University, Lancaster LA1 4YB, UK.
⁴³Institut fur Physik, Humboldt-Universitat zu Berlin, Newtonstrasse 15, D-12489 Berlin, Germany.
⁴⁴Zentrum für Astronomie der Universität Heidelberg, Institut für Theoretische Astrophysik, Philosophenweg 12, 69120 Heidelberg, Germany.
⁴⁵Heidelberger Institut für Theoretische Studien, Schloss-Wolfsbrunnenweg 35, 69118 Heidelberg, Germany.
⁴⁶Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Väisäläntie 20, 21500 Piikkiö, Finland.
⁴⁷Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany.
⁴⁸Sorbonne Universités, UPMC Université Paris 6 and CNRS, UMR 7095, Institut d'Astrophysique de Paris, 98 bis boulevard Arago, 75014 Paris, France.
⁴⁹INAF-Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy.
⁵⁰Department of Astrophysics, University of Oxford, Oxford OX1 3RH, UK.
⁵¹Università degli studi di Catania, DFA DIEEI, Via Santa Sofia 64, 95123 Catania, Italy.
⁵²INFN-Laboratori Nazionali del Sud, Via Santa Sofia 62, 95123 Catania, Italy.
⁵³Department of Astronomy, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago de Chile, Chile.
⁵⁴Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218, USA.
⁵⁵Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA.
⁵⁶Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune 411007, India.
⁵⁷School of Physical, Environmental, and Mathematical Sciences, University of New South Wales, Australian Defence Force Academy, Canberra, Australian Capital Territory 2600, Australia.
⁵⁸Research School of Astronomy and Astrophysics, The Australian National University, Canberra, Australian Capital Territory 2611, Australia.
⁵⁹ARC Centre of Excellence for All-sky Astrophysics (CAASTRO).
⁶⁰LSST, 950 North Cherry Avenue, Tucson, Arizona 85719, USA.
⁶¹Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
⁶²Department of Physics, University of the Free State, Bloemfontein 9300, South Africa.
⁶³Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA.
⁶⁴School of Physics and Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, Minnesota 55455-0149, USA.

⁰Astrophysics Research Centre, School of Mathematics and Physics, Queens University Belfast, Belfast BT7 1NN, UK.

Nature +

|

November 3, 2017

View abstract on PubMed

Summary

Binary neutron-star mergers produce gravitational waves and kilonovae. These events eject heavy elements, powering an electromagnetic signal consistent with r-process nucleosynthesis, confirming their role in creating elements heavier than iron.

Area Of Science

Astrophysics
Nuclear Astrophysics
Gravitational Wave Astronomy

Background

Gravitational waves (GWs) were initially detected from binary black-hole mergers.
Neutron-star mergers are predicted to produce GWs and eject radioactive material.
This ejected material can power a luminous electromagnetic signal known as a kilonova.

Purpose Of The Study

To report observations of an electromagnetic transient coincident with a binary neutron-star merger (GW170817).
To model the physical parameters of the transient and compare them with theoretical kilonova predictions.
To investigate the nucleosynthetic origin of heavy elements produced in neutron-star mergers.

Main Methods

Observations of the transient event in the galaxy NGC 4993, spatially coincident with GW170817.
Physical modeling of the observed electromagnetic radiation, including ejected mass, opacity, velocity, and power source.
Spectroscopic analysis to identify elemental composition and compare with r-process nucleosynthesis predictions.

Main Results

Detection of a rapidly fading electromagnetic transient (kilonova) spatially coincident with GW170817 and a weak gamma-ray burst.
Physical parameters (ejected mass ~0.04 solar masses, low opacity, high velocity) broadly match blue kilonova predictions.
Power-law slope of the light curve (-1.2 ± 0.3) is consistent with radioactive powering from r-process nuclides.
Spectral features suggest the presence of light r-process elements (atomic masses 90-140).
Observed rapid fading and reddening indicate a possible contribution from lanthanide-rich ejecta.

Conclusions

Binary neutron-star mergers generate both gravitational waves and radioactively powered kilonovae.
These mergers are confirmed as a significant nucleosynthetic source of r-process elements, heavier than iron.
The observed kilonova provides direct evidence for the production of heavy elements in these cosmic events.

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