After several months of thorough analysis, the LIGO Scientific Collaboration \u2014in which the Galician Institute of High Energy Physics (IGFAE) participates\u2014 and the Virgo Collaboration have released an updated catalog of gravitational wave detections. The catalog contains 39 new signals from black-hole or neutron-star collisions detected between April 1\u2014Oct 1, 2019, which more than triples the number of confirmed detections.\u00a0 \u00a0 The new set includes some of the most interesting systems we have seen so far, and enables qualitatively new studies of astrophysical populations and fundamental physics.<\/p>\n
The sharp increase in the number of detections was made possible by significant improvements to the instruments with respect to previous observation periods. \u00a0 These included increased laser power, improved mirrors and, remarkably, the use of quantum squeezing technology.\u00a0 All together, these enhancements resulted in a ~60% improvement in the range to which signals can be detected.\u00a0 The detectors were also able to operate without interruption more often than in the past, with an improved duty cycle of ~75% vs ~60%.<\/p>\n
With all of these new signals, we can begin to better understand the populations of black holes and neutron stars. \u00a0 By analyzing the entire population of binary black hole mergers simultaneously we can maximize the astrophysical information we extract. \u00a0 We infer that the distribution of black hole masses does not follow a simple power-law distribution. \u00a0 Measuring the deviations from this power law will enable us to learn about the formation of these black holes, either as the result of stellar deaths or previous collisions.\u00a0 Considering the entire population together also allows us to make stronger measurements of difficult to measure properties such as black hole spin. We find that some merging black holes have spins which are misaligned with their orbital angular momentum. This will allow us to probe the regimes in which these binaries formed.<\/p>\n
We can also use the many signals in the updated catalog to put Einstein\u2019s theory of gravity to the test in more and better ways than before. \u00a0 This was done by comparing the data against predictions from the theory and constraining possible deviations. \u00a0 The results from multiple signals were combined using new statistical methods to obtain the tightest constraints so far on the properties of gravity in the strong, highly-dynamical regime of black hole mergers.\u00a0 With the new catalog, LIGO and Virgo were also able to directly study the properties of the remnant objects produced during the mergers: by measuring the vibrations of these objects, and by ruling out potential \u201cechoes\u201d after the main signals, LIGO and Virgo confirmed that the remnants behaved as we expect from black holes in Einstein\u2019s theory.<\/p>\n
The results reported in the new catalog correspond to only the first six months of LIGO and Virgo\u2019s third observing run. Results from the remaining five months are currently being analyzed. In the meantime, the LIGO and Virgo instruments are undergoing upgrades in preparation for the fourth observing run, for which they will be also joined by the KAGRA detector in Japan. More exciting discoveries are on the horizon.<\/p>\n
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