Multi-messenger Observations of a Binary Neutron Star Merger

AGILE Team, ALMA Collaboration, ANTARES Collaboration, ASKAP Australian SKA Pathfinder, AstroSat Cadmium Zinc Telluride Imager Team, ATCA: Australia Telescope Compact Array, ATLAS, BOOTES Collaboration, CALET Collaboration, Chandra Team at McGill University, Dark Energy Camera GW-EM, DFN Desert Fireball Network, DLT40 Collaboration, ePESSTO, Euro VLBI Team, Fermi GBM Collaboration, Fermi Large Area Telescope Collaboration, GRAvitational Wave Inaf TeAm (GRAWITA), GROWTH JAGWAR CALTECH, H.E.S.S. CollaborationHAWC Collaboration, High Time Resolution Universe Survey, Icecube Collaboration, IKI-GW Follow-up Collaboration, Insight-HXMT Collaboration, IPN Collaboration, J-GEM Collaboration, KU Collaboration, Las Cumbres Observatory Group, LIGO Scientific Collaboration, Virgo Collaboration, Low Frequency Array (LOFAR) Collaboration, LWA Long Wavelength Array, MASTER Collaboration, MAXI Collaboration, Murchison Wide-field Array (MWA) Collaboration, Nordic Optical Telescope, OzGrav Collaboration, Pan-STARRS Collaboration, Pi of the Sky Collaboration, Pierre Auger Collaboration, RIMAS and RATIR, SALT Group, SKA South Africa/MeerKAT, Swift Collaboration, Texas Tech University, The 1M2H Team, Transient Robotic Observatory of the South (TOROS) Collaboration, TZAC Consortium, VINROUGE Collaboration, INTEGRAL Collaboration, Deeper, Wider, Faster program (DWF)

Research output: Contribution to journalArticleAcademicpeer-review


On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of similar to 1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg(2) at a luminosity distance of 40(-8)(+8) Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 M-circle dot. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at similar to 40 Mpc) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over similar to 10 days. Following early non-detections, X-ray and radio emission were discovered at the transient''s position similar to 9 and similar to 16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta.
Original languageEnglish
Article numberL12
Number of pages59
JournalAstrophysical Journal Letters
Issue number2
Publication statusPublished - 20 Oct 2017
Externally publishedYes


  • gravitational waves
  • stars: neutron


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