We report the observation of a compact binary coalescence involving a 22.2–24.3 M⊙ black hole and a compact object with a mass of 2.50–2.67 M⊙ (all measurements quoted at the 90% credible level). The gravitational-wave signal, GW190814, was observed during LIGO's and Virgo's third observing run on 2019 August 14 at 21:10:39 UTC and has a signal-to-noise ratio of 25 in the three-detector network. The source was localized to 18.5 deg2 at a distance of 241+41-45 Mpc; no electromagnetic counterpart has been confirmed to date. The source has the most unequal mass ratio yet measured with gravitational waves, 0.112+0.008-0.009, and its secondary component is either the lightest black hole or the heaviest neutron star ever discovered in a double compact-object system. The dimensionless spin of the primary black hole is tightly constrained to ≤0.07. Tests of general relativity reveal no measurable deviations from the theory, and its prediction of higher-multipole emission is confirmed at high confidence. We estimate a merger rate density of 1–23 Gpc−3 yr−1 for the new class of binary coalescence sources that GW190814 represents. Astrophysical models predict that binaries with mass ratios similar to this event can form through several channels, but are unlikely to have formed in globular clusters. However, the combination of mass ratio, component masses, and the inferred merger rate for this event challenges all current models of the formation and mass distribution of compact-object binaries.
History
Publication title
The Astrophysical Journal Letters
Volume
896
Article number
L44
Number
L44
ISSN
2041-8205
Department/School
School of Natural Sciences
Publisher
Institute of Physics Publishing Ltd.
Place of publication
United Kingdom
Rights statement
Copyright (2020) The American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 Unported (CC BY 3.0) licence (https://creativecommons.org/licenses/by/3.0/).