Observation of Gravitational Waves from a Binary Black Hole Merger

Abstract

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0 × 10 −21 . It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410 These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

Observing gravitational-wave transient GW150914 with minimal assumptions

“…The three panels of the figure correspond to three bins of effective spin. Effective spin is defined as in [29]: χ eff ¼ ð…”

“…The black hole spins are obtained from the dimensionless spin vectors by S i ¼ m 2 i a i , where ja i j ≤ 1. The simulation includes binaries that are isotropically located on the sky and isotropically oriented, with total masses M ¼ m 1 þ m 2 uniformly distributed between 30 and 150 M ⊙ , that is within a factor of ∼2 of the estimated total mass for GW150914 [29]. We generate three separate sets, each with a fixed mass ratio q ¼ m 2 =m 1 ∈ f0.25; 0.5; 1.0g.…”

“…In [29], we present estimates for the parameters of the binary black hole model that best describes GW150914. These parameters include the masses and spins of the binary components, and their posterior distributions represent our most complete description of the astrophysical source.…”

“…Burst localization algorithms produce systematically larger skymaps than template-based algorithms because they make fewer assumptions about the waveform. However, the LALInference map reported here also includes the effects of calibration uncertainty within the detectors, which significantly widen the uncertainty of this reconstruction [45]. In principle, calibration effects could also be included in the burst skymaps, but what is shown here represents the information that was available at the time electromagnetic astronomy observations began [28].…”

“…Two days after the signal was found, a notice with the estimated source position was sent to a consortium of astronomers to search for possible counterparts [28]. Investigations continued over the next several months to validate the observation, estimate its statistical significance, and characterize the astrophysical source [29,30].…”