GW151226: Observation of Gravitational Waves from a 22-Solar-Mass Binary Black Hole Coalescence (1606.04855v1)

Abstract: We report the observation of a gravitational-wave signal produced by the coalescence of two stellar-mass black holes. The signal, GW151226, was observed by the twin detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) on December 26, 2015 at 03:38:53 UTC. The signal was initially identified within 70 s by an online matched-filter search targeting binary coalescences. Subsequent off-line analyses recovered GW151226 with a network signal-to-noise ratio of 13 and a significance greater than 5 $\sigma$. The signal persisted in the LIGO frequency band for approximately 1 s, increasing in frequency and amplitude over about 55 cycles from 35 to 450 Hz, and reached a peak gravitational strain of $3.4_{-0.9}^{+0.7} \times 10^{-22}$. The inferred source-frame initial black hole masses are $14.2_{-3.7}^{+8.3} M_{\odot}$ and $7.5_{-2.3}^{+2.3} M_{\odot}$ and the final black hole mass is $20.8_{-1.7}^{+6.1} M_{\odot}$. We find that at least one of the component black holes has spin greater than 0.2. This source is located at a luminosity distance of $440_{-190}^{+180}$ Mpc corresponding to a redshift $0.09_{-0.04}^{+0.03}$. All uncertainties define a 90 % credible interval. This second gravitational-wave observation provides improved constraints on stellar populations and on deviations from general relativity.

• The paper reports the detection of gravitational waves from a binary black hole merger with >5σ significance and an SNR of 13.
• The analysis employed rigorous matched-filtering and Bayesian techniques using post-Newtonian and numerical relativity waveform models to estimate black hole spins and masses.
• The study confirms Einstein’s theory by constraining general relativity in the dynamic regime and advancing our understanding of stellar evolution and black hole formation.

Observation of Gravitational Waves from a 22-Solar-Mass Binary Black Hole Coalescence: An Expert Overview

The paper reports the detection of a gravitational-wave signal, designated GW151226, originating from the coalescence of two stellar-mass black holes. This event was observed by the Laser Interferometer Gravitational-Wave Observatory (LIGO) on December 26, 2015. The significance of this observation lies in its confirmation of the existence and detectability of gravitational waves from stellar-mass black hole mergers, as initially predicted by Einstein over a century ago.

Key Observational Details

The GX151226 signal was detected with a significant network signal-to-noise ratio (SNR) of 13 and a statistical significance greater than 5σ. It persisted in the detectable frequency band for approximately one second, with the frequency increasing from 35 Hz to 450 Hz. The gravitational strain at peak amplitude was 3.4+0.7×10^-22. The source’s estimated location is at a luminosity distance of 440 Mpc with a corresponding redshift of 0.09. This configuration suggests a binary system comprising black holes with source-frame masses of 14.2+8.3M⊙ and 7.5+2.3M⊙, respectively, merging into a final black hole, radiating 1.0±0.2M⊙ of energy.

Methodological Rigor

The detection and analysis of GW151226 employed matched-filtering techniques, which proved essential given the signal’s relatively modest strain amplitude. The signal extraction and parameter estimation processes were rigorously cross-validated against instrumental noise sources and employed advanced waveform models derived from post-Newtonian theory, effective-one-body formalism, and numerical relativity.

The Bayesian analysis utilized two distinct waveform models accounting for spin-induced precession and aligned-spin assumptions. This analysis confirmed that at least one black hole in the binary system exhibited a dimensionless spin magnitude greater than 0.2, a non-trivial finding that has profound implications for understanding black hole formation and evolution.

Astrophysical and Theoretical Implications

The implication of detecting a gravitational-wave signal from a binary black hole provides crucial insights into stellar evolution, black hole formation mechanisms, and the dynamics of compact binary systems. The observation of GW151226, alongside earlier detections, enables improved constraints on stellar black hole mass distributions and enhances understanding of binary black hole demographics, including potential spin alignment characteristics.

Furthermore, the observation supports general relativity as the governing theory of gravitation even in the highly dynamical regime of black hole mergers. The constraints obtained from post-Newtonian coefficients have shown remarkable consistency with the predictions of general relativity, reinforcing its applicability at cosmic scales.

Future Perspectives

The continued operation and improvement of LIGO promise further insights into cosmic events involving black holes and neutron stars. Future advancements in detector sensitivity will not only refine distance and parameter estimates but also enhance the ability to measure spin precession effects, providing additional data for testing modifications to gravitational theory and probing the assembly history of black holes.

As the field of gravitational-wave astronomy matures, the detection rate of such events is expected to increase, thereby contributing to a deeper cosmological understanding of black hole populations and offering potential to collaborate with electromagnetic observations, enriching our comprehension of transient cosmic phenomena.