GW150914

GW150914
B. P. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration) — fu · CC BY 3.0 · source
Name	GW150914
Caption	First direct detection of gravitational waves announced by LIGO Scientific Collaboration and Virgo partners at LSC-Virgo press conferences
Date	2015-09-14
Detector	LIGO Hanford, LIGO Livingston
Significance	5.1 sigma
Distance	~410 Mpc
Mass1	~36 M☉
Mass2	~29 M☉
Remnant mass	~62 M☉
Energy radiated	~3 M☉c²
Announced	2016-02-11

GW150914 was the first direct detection of gravitational waves and the first observation of a binary black hole merger announced by the LIGO Scientific Collaboration and the Virgo Collaboration. The event, recorded on 2015-09-14 by the Hanford and Livingston detectors, provided the first empirical confirmation of a key prediction of Albert Einstein's General relativity and inaugurated gravitational-wave astronomy. The discovery tightly connected communities including the LIGO Scientific Collaboration, Caltech, Massachusetts Institute of Technology, and international partners such as Albert Einstein Institute.

Discovery and detection

The signal was first identified in near-real time by pipelines developed by the LIGO Scientific Collaboration, involving teams at Caltech, MIT, University of Florida, University of Wisconsin–Milwaukee, Columbia University, Cardiff University, and University of Glasgow. The matched-filter search pipelines used waveform models created by researchers at Max Planck Institute for Gravitational Physics, Penn State University, Rochester Institute of Technology, Georgia Institute of Technology, and Northwestern University. The event was recorded at the Livingston detector and 7 ms later at the Hanford detector, with significance assessed by teams at LIGO Laboratory, Kavli Institute for Theoretical Physics, and Perimeter Institute.

Source and progenitor black holes

Parameter inference attributed the signal to a coalescence of two stellar-mass black holes with masses estimated by analysis groups at Caltech, MIT, AEI, Cardiff University, and Monash University. The binary components were inferred to have source-frame masses of roughly 36 and 29 solar masses, producing a remnant black hole of about 62 solar masses; the missing mass-energy (~3 M☉) was radiated in gravitational waves. The progenitor system’s properties were discussed in context by theorists at University of Cambridge, Princeton University, Yale University, University of Tokyo, and University of Chicago who considered formation channels including isolated binary evolution and dynamical assembly in environments such as globular clusters studied by researchers at Northwestern University and University of Sussex.

Signal analysis and parameter estimation

Waveform modeling combined post-Newtonian expansions and numerical relativity produced by groups at Caltech, AEI, Perimeter Institute, Cornell University, and University of Birmingham. Parameter estimation used Bayesian techniques implemented by teams at Cardiff University, University of Glasgow, Max Planck Institute for Gravitational Physics, MIT, and Caltech. Analyses constrained masses, spins, luminosity distance, and sky localization, with sky maps produced collaboratively by LIGO Scientific Collaboration and Virgo Collaboration scientists at NASA Goddard Space Flight Center and Australian National University. Statistical significance was validated using background estimation methods developed at LIGO Laboratory, University of Wisconsin–Milwaukee, and Stanford University.

Astrophysical implications and tests of general relativity

The observation provided empirical support for predictions by Albert Einstein and enabled tests of General relativity in the strong-field, highly dynamical regime. Constraints on deviations from general relativity were reported by groups at Caltech, MIT, AEI, and Perimeter Institute, comparing inspiral, merger, and ringdown phases to analytic and numerical templates from Numerical relativity teams at University of Southampton, RIT (Rochester Institute of Technology), and Cambridge University. The event influenced population studies by researchers at University of Maryland, Columbia University, University of Oxford, Leiden University, and Monash University examining black hole mass distributions, stellar evolution models from Geneva Observatory groups, and cosmological implications discussed by scientists at Harvard University and Princeton University.

Instrumentation and data processing

The detection relied on kilometer-scale interferometers built and operated by LIGO Laboratory with significant contributions from Caltech and MIT, and upgrades implemented with teams from European Gravitational Observatory, AEI, Australian National University, and University of Glasgow. Key subsystems were developed by groups at Jet Propulsion Laboratory, Stanford University, University of Birmingham, Cardiff University, and Syracuse University. Data conditioning, calibration, and noise characterization involved collaborations with LIGO Hanford Observatory, LIGO Livingston Observatory, Perimeter Institute, LIGO Scientific Collaboration working groups, and computational resources at LIGO Data Grid, XSEDE, and National Energy Research Scientific Computing Center.

Follow-up observations and electromagnetic searches

Extensive follow-up campaigns coordinated by the LIGO Scientific Collaboration and Gamma-ray Coordinates Network engaged observatories including Fermi Gamma-ray Space Telescope, INTEGRAL, Swift, Pan-STARRS, Dark Energy Survey, Very Large Array, Australia Telescope Compact Array, Optical Gravitational Lensing Experiment, Subaru Telescope, and Keck Observatory. No confirmed electromagnetic counterpart was associated, though candidate signals such as a marginal transient reported by Fermi Gamma-ray Space Telescope sparked multi-team analysis by groups from NASA, ESA, CSIRO, University of Tokyo, and University of Geneva.

Category:Gravitational-wave astronomy Category:Black hole mergers