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[superscript +8.4] [subscript −6.0]M⊙ and 19.4 [superscript +5.3] [subscript −5.9]M⊙ (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,
χ [subscript eff] = −0.12[superscript +0.21] [subscript −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 [superscript +450] [subscript −390] Mpc corresponding to a redshift of z = 0.18[superscript +0.08][subscript −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[subscript g] ≤ 7.7 × 10 [superscript −23] eV/c[superscript 2]. In all cases, we find that GW170104 is consistent with general relativity.