LIGO-Virgo Update

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Sky & Telescope

The LIGO and Virgo collaborations recently released their second official catalog of gravitational-wave detections, raising the total number of collisions from 11 to 50. Of these events, nearly all were pairs of black holes merging.

The new 39 detections come from the first six months of the collaboration’s third observing run, or O3, which ran from April to October 2019. Several of the O3 events have already made headlines, announced on their own over the course of 2020.


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The total number of LIGO/Virgo black hole (blue) and neutron star (orange) merger events detected between September 2015 and October 2019, as reported by the joint collaboration
Credit: LIGO-Virgo / Northwestern U / Frank Elavsky & Aaron Geller


Population properties of compact objects from the second LIGO–Virgo Gravitational-Wave Transient Catalog

We report on the population properties of the 47 compact binary mergers in GWTC-2, including all Advanced LIGO–Virgo observing runs through the most recent observing run O3a. We investigate the mass distribution, spin distribution, and merger rate as a function of redshift.
  • While the primary mass distribution must extend to ∼ 65 M_s or beyond, only 2.9 +3.4/−1.7% of systems have primary masses greater than 45 M_s. At low masses, we find that the primary mass spectrum has a global maximum at 7.8 +2.2/−2.1 M_s, consistent with a gap between ∼ 2.6 M_s and ∼ 6 M_s.
  • Second, we find evidence that a nonzero fraction of BBH systems have component spins misaligned with the orbital angular momentum, giving rise to precession of the orbital plane. Moreover, we infer that 12% to 44% of BBH systems have spins tilted by more than 90° with respect to their orbital angular momentum, giving rise to a negative effective inspiral spin parameter.
 
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