The Institute for High Energy Physics (IFAE), a BIST centre, is part of the Virgo and LIGO collaborations which detected 35 new events in their latest observation period, bringing the total number of gravitational waves detected to ninety.
Thirty-five new events detected by LIGO and Virgo in their latest observation period bring the total number of gravitational waves detected to ninety. These events are spacetime quakes generated by the mergers of either two black holes or neutron stars, or black hole-neutron star pairs. The dataset, published today in the so-called third Catalog Paper, outlines the features of new populations of black holes, the masses of which, together with those of the observed neutron stars, provide clues about how stars live and die, further broadening the horizons of gravitational astronomy.
Most of the new signals originate from the whirling spiral of two merging black holes: cosmic quakes that shake the fabric of spacetime, generating a powerful burst of gravitational waves. Two other events, one already reported last June, were instead identified as mergers between a neutron star and a black hole, a source observed for the first time in this last LIGO-Virgo run. A further event, detected in February, 2020, could come from either a pair of black holes or from a mixed pair of a black hole with a neutron star.
The dataset, published this month in the so-called third Catalog Paper, outlines the features of new populations of black holes, the masses of which, together with those of the observed neutron stars, may provide clues about how stars live and die, further broadening the horizons of gravitational astronomy.
The Catalog is accompanied by three other publications, focusing on the cosmological and astrophysical consequences of the results and on the multi-messenger search for gravitational-wave signals in coincidence with 86 very energetic bursts (Gammy Ray Bursts) detected in space by the Fermi/GBM and Swift/BAT instruments during the second part of the third observation period. No confident Gravitational Wave counterparts have been observed; in parallel, no signals of a different kind (e.g. light and neutrinos) have thus far been reported by telescopes and observatories on Earth or in space following-up the Gravitational Wave signals.
At the same time, the LIGO, Virgo, and KAGRA scientific collaborations have also released the full set of calibrated data recorded by the LIGO and Virgo detectors from November, 2019 to March, 2020. This will allow the entire research community to perform independent analyses and checks, maximising the wealth of scientific results.
The progress achieved in a few years by gravitational-wave scientists has been amazing, going from the first detection to the observation of a number of events per month. This has been possible thanks to the programme of continuous technological upgrades, which have transformed the first pioneering instruments into increasingly sensitive detectors. The progress in detector sensitivity due to the technological upgrades and commissioning is evident, considering that, of the 90 gravitational-wave events published this month, as many as 79 refer exclusively to the most recent observation period, which ran from April, 2019 to March, 2020.
The LIGO and Virgo observatories are currently undergoing a further upgrade and will start the upcoming fourth observing period in the second half of 2022, with an even greater sensitivity, corresponding to a volume of the Universe almost 10 times larger than before and, therefore, a much greater probability of picking up gravitational signals.
“Among the other upgrades at Virgo, we have realised an additional optical cavity (the so-called signal-recycling cavity), which allows to improve the sensitivity band of the detector at high frequencies”, said Sebastian Steinlechner, assistant professor at Maastricht University and Nikhef. “This corresponds to an increased capacity of the detector to ‘listen’ to the final stages of the coalescing pairs, when two black holes or stars merge into one.”
More information can be found on the IFAE website.