Multi-messenger Observations of a Binary Neutron Star Merger

THE PIERRE AUGER COLLABORATION.; S. J. SCIUTTO

The Astrophysical Journal Letters

IOP Publishing

Año: 2017 vol. 848 p. 12 - 70

2041-8213

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. TheFermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a skyregion of 31 deg2 at a luminosity distance of 40 88-+ Mpc and with component masses consistent with neutron stars. Thecomponent masses were later measured to be in the range 0.86 to 2.26 M. An extensive observing campaign waslaunched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now withthe IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the OneMeter,Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independentlydetected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Earlyultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed aredward evolution over ∼10 days. Following early non-detections, X-ray and radio emission were discovered atthe transient?s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likelyarise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. Noultra-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 inNGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by theradioactive decay of r-process nuclei synthesized in the ejecta.