GW170817 — LLMpedia

GW170817
Name	GW170817
Type	Binary neutron star merger
Discovery date	2017-08-17
Detectors	LIGO, Virgo
Electromagnetic counterparts	GRB 170817A, AT 2017gfo
Host	NGC 4993

Contents

GW170817 GW170817 was a landmark transient first identified by interferometric observatories on 17 August 2017 and rapidly associated with a short gamma-ray burst and a kilonova, inaugurating the era of multimessenger astronomy. The event linked observations from facilities associated with LIGO Scientific Collaboration, Virgo, Fermi Gamma-ray Space Telescope, INTEGRAL, and numerous optical, radio, and X-ray observatories, enabling joint constraints on nuclear physics, relativity, and cosmology. The detection prompted coordinated campaigns from institutions including European Southern Observatory, Space Telescope Science Institute, National Radio Astronomy Observatory, Max Planck Society, and major universities worldwide.

Discovery and detection

The initial gravitational-wave trigger was registered by the LIGO Hanford Observatory and LIGO Livingston Observatory networks with contemporaneous lower-significance data from Virgo, followed within seconds by a gamma-ray flash reported by Fermi Gamma-ray Space Telescope and INTEGRAL. Rapid notices were circulated through channels used by Gamma-ray Burst Coordinates Network and observatories such as Pan-STARRS, Dark Energy Camera, Subaru Telescope, and VLT enabling identification of an optical counterpart. Follow-up teams from Keck Observatory, Gemini Observatory, Hubble Space Telescope, Chandra X-ray Observatory, Very Large Array, Atacama Large Millimeter/submillimeter Array, and Karl G. Jansky Very Large Array coordinated multiwavelength coverage. The discovery galvanized organizations like National Science Foundation, European Research Council, NASA, and research groups at Caltech, MIT, University of Cambridge, and University of Tokyo.

Analysis indicated the progenitor was a compact binary consistent with two neutron stars in a inspiral comparable to systems observed in the Hulse–Taylor binary class and analogous to pulsars cataloged by Arecibo Observatory and Parkes Observatory. Mass estimates invoked equations-of-state studied by groups at CERN, Oak Ridge National Laboratory, and Lawrence Berkeley National Laboratory and engaged nuclear theory groups linked to Institute for Nuclear Theory and Rutherford Appleton Laboratory. The merger dynamics were modeled using numerical relativity codes developed by teams at NASA Ames Research Center, Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Princeton University, and Columbia University, drawing on microphysics explored at Brookhaven National Laboratory and Los Alamos National Laboratory.

The gravitational waveform matched post-Newtonian templates and numerical-relativity extensions produced by collaborations including LIGO Scientific Collaboration, Einstein Telescope concept studies, and groups at University of Illinois Urbana–Champaign and University of Birmingham. Parameter estimation used software frameworks like LALSuite and Bayesian pipelines developed in cooperation with groups at Perimeter Institute and Flatiron Institute. The signal enabled measurement of tidal deformability tied to the nuclear EOS investigated by Max Planck Institute for Astrophysics and constraints on the speed of gravity compared to light comparable to limits discussed by Albert Einstein Institute and Stephen Hawking-related theoretical programs.

A short gamma-ray burst, cataloged as GRB 170817A, was detected by Fermi Gamma-ray Space Telescope and INTEGRAL and associated with the event by teams at NASA Goddard Space Flight Center and European Space Agency. The optical/infrared transient AT 2017gfo was identified by observers from Swope Telescope and Chilean La Silla Observatory then spectroscopically characterized with instruments on Gemini Observatory, Keck Observatory, and VLT. Photometry and spectroscopy implicated r-process nucleosynthesis hypotheses advanced by researchers connected to Princeton Plasma Physics Laboratory and Max Planck Institute for Extraterrestrial Physics, supporting kilonova models developed by teams at University of Copenhagen and Caltech. X-ray and radio afterglow evolution was monitored by Chandra X-ray Observatory and Very Large Array, informing jet-structure models from groups at Stanford University and University of Amsterdam.

Localization algorithms combined sky maps from LIGO Scientific Collaboration and Virgo with galaxy catalogs curated by Sloan Digital Sky Survey and Two Micron All-Sky Survey, leading to identification of the elliptical galaxy NGC 4993 in the Fornax Cluster region. Observatories such as Hubble Space Telescope, ESO, and Gemini Observatory imaged host morphology and stellar populations, enabling comparisons to host studies of short gamma-ray bursts cataloged by teams at Harvard–Smithsonian Center for Astrophysics and University of Leicester. Distance estimates were cross-checked using redshift measures from Sloan Digital Sky Survey and local flow models informed by work at Arecibo Observatory and 2MASS Redshift Survey efforts.

Combined gravitational-wave and electromagnetic data provided a novel standard-siren measurement of the Hubble constant, debated among groups at Planck Collaboration, Supernova Cosmology Project, SH0ES Team, and Dark Energy Survey. Constraints on the neutron-star equation of state influenced studies at CERN and National Institute for Nuclear Physics (INFN), while the connection to r-process element production linked to chemical-evolution work from Max Planck Institute for Astronomy and Carnegie Institution for Science. Tests of general relativity and Lorentz invariance were contextualized by research at Perimeter Institute, Institute for Advanced Study, and theoretical groups inspired by Albert Einstein and Roger Penrose-related legacies.

Long-term monitoring by Chandra X-ray Observatory, Very Large Array, ALMA, Hubble Space Telescope, and ground-based facilities informed jet-cocoon and remnant evolution models pursued at Caltech, MIT, University of California, Berkeley, and Instituto de Astrofísica de Canarias. GW170817 catalyzed upgrades to LIGO, plans for Einstein Telescope, and proposals for missions such as LISA and enhanced gamma-ray observatories, and inspired policy and funding initiatives at National Science Foundation, European Research Council, and NASA. The event features in outreach and education programs by Smithsonian Institution, American Astronomical Society, Royal Astronomical Society, and remains a focal case in multidisciplinary studies spanning institutions like University of Oxford, Yale University, Princeton University, and University of Chicago.