# GW170104: Observation of a 50-Solar-Mass Binary Black Hole Coalescence at Redshift 0.2

## TL;DR

The paper reports the detection and analysis of GW170104, a gravitational wave from a binary black hole merger at redshift 0.2, providing insights into black hole properties, testing general relativity, and constraining graviton mass.

## Contribution

First detailed analysis of GW170104, including black hole masses, spins, distance, and tests of gravitational theories, expanding understanding of stellar-mass black hole mergers.

## Key findings

- Black hole masses are approximately 31.2 and 19.4 solar masses.
- Effective inspiral spin parameter suggests spins are not both aligned positively.
- Graviton mass constrained to less than 7.7 x 10^{-23} eV/c^2.

## Abstract

We describe the observation of GW170104, a gravitational-wave signal produced by the coalescence of a pair of stellar-mass black holes. The signal was measured on January 4, 2017 at 10:11:58.6 UTC by the twin advanced detectors of the Laser Interferometer Gravitational-Wave Observatory during their second observing run, with a network signal-to-noise ratio of 13 and a false alarm rate less than 1 in 70,000 years. The inferred component black hole masses are $31.2^{+8.4}_{-6.0}\,M_\odot$ and $19.4^{+5.3}_{-5.9}\,M_\odot$ (at the 90% credible level). The black hole spins are best constrained through measurement of the effective inspiral spin parameter, a mass-weighted combination of the spin components perpendicular to the orbital plane, $\chi_\mathrm{eff} = -0.12^{+0.21}_{-0.30}.$ This result implies that spin configurations with both component spins positively aligned with the orbital angular momentum are disfavored. The source luminosity distance is $880^{+450}_{-390}~\mathrm{Mpc}$ corresponding to a redshift of $z = 0.18^{+0.08}_{-0.07}$. We constrain the magnitude of modifications to the gravitational-wave dispersion relation and perform null tests of general relativity. Assuming that gravitons are dispersed in vacuum like massive particles, we bound the graviton mass to $m_g \le 7.7 \times 10^{-23}~\mathrm{eV}/c^2$. In all cases, we find that GW170104 is consistent with general relativity.