GW170608: Observation of a 19 Solar-mass Binary Black Hole Coalescence

TLDR

The component masses fall within the range of low‑mass X‑ray binary black holes, enabling comparison between gravitational‑wave and electromagnetic observations. On 8 June 2017, Advanced LIGO detected GW170608, the lightest known binary black‑hole merger with component masses 12⁺⁷₋₂ M⊙ and 7⁺²₋₂ M⊙, a luminosity distance of 340⁺¹⁴⁰₋₁₄₀ Mpc (z ≈ 0.07), and a waveform fully consistent with general relativity.

Abstract

On June 8, 2017 at 02:01:16.49 UTC, a gravitational-wave signal from the merger of two stellar-mass black holes was observed by the two Advanced LIGO detectors with a network signal-to-noise ratio of 13. This system is the lightest black hole binary so far observed, with component masses $12^{+7}_{-2}\,M_\odot$ and $7^{+2}_{-2}\,M_\odot$ (90% credible intervals). These lie in the range of measured black hole masses in low-mass X-ray binaries, thus allowing us to compare black holes detected through gravitational waves with electromagnetic observations. The source's luminosity distance is $340^{+140}_{-140}$ Mpc, corresponding to redshift $0.07^{+0.03}_{-0.03}$. We verify that the signal waveform is consistent with the predictions of general relativity.