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A Cornucopia of Newly Confirmed Gravitational Wave Detections

A Cornucopia of Newly Confirmed Gravitational Wave Detections

After months of thorough analysis, two international scientific teams, including scientists from The University of Texas at Austin, have released an updated catalog of gravitational wave detections, more than tripling the number of confirmed events. Each detection of a gravitational wave represents the discovery of a pair of extremely massive objects—black holes or neutron stars—far out in the universe smashing into each other, shaking the very fabric of space and time so much that sensitive detectors on Earth could feel them, sometimes more than a billion years later. 

The catalog contains 39 new signals detected by the LIGO Scientific Collaboration and the Virgo Collaboration between April 1 and Oct 1, 2019. The new set includes some of the most interesting systems scientists have seen so far, and enables qualitatively new studies of astrophysical populations and fundamental physics.

A series of four papers describing the catalog and analyzing the new data were published online this week on the preprint server arXiv (see links below), in advance of publication in peer-reviewed journals. Authors of the studies include professor Deirdre Shoemaker and assistant professor Aaron Zimmerman, both in UT Austin's Department of Physics, along with visiting scholar Deborah Ferguson, postdoctoral researchers Cody Messick and Jacob Lange, and graduate students María José Bustamante Rosell and Richard George.

Watch an animation of the newly confirmed binary black hole mergers

The updated catalog includes four especially noteworthy events: the heaviest black hole binary system detected so far; two black holes with very different masses; the second detection of a binary neutron star merger; and the merger of a black hole with a curious object that is either the lightest black hole or heaviest neutron star so far detected.

Analyzing the entire population of binary black hole mergers at once also is allowing for new insights. For example, scientists are exploring different hypotheses for how binary black holes form.

"The big puzzle we are trying to solve is whether these binary black holes are coming from the evolution of pairs of stars born together," Zimmerman said, "or whether black holes that are initially independent of each other form binaries later because they live in very dense environments where they are being flung around by other black holes all the time."

Based on the updated catalog, the LIGO and Virgo teams discovered that some merging binary black holes have spins that are misaligned with the plane of their orbit, suggesting that some of the binaries may be formed by the second of the two processes. While the results are not yet definitive, future observations might confirm this interpretation.

With all of these new signals, scientists can begin to better understand the populations of black holes and neutron stars. They can also use the many signals in the updated catalog to put Einstein's theory of gravity to the test in new ways. So far, LIGO and Virgo have confirmed that the remnant black holes behaved as expected for black holes in Einstein's theory.

The results reported in the new catalog correspond to only the first six months of LIGO and Virgo's 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 likely on the horizon.

Four papers describing and analyzing the updated catalog:

Compact Binary Coalescences Observed by LIGO and Virgo During the First Half of the Third Observing Run

Population Properties of Compact Objects from the Second LIGO-Virgo Gravitational-Wave Transient Catalog

Tests of General Relativity with Binary Black Holes from the second LIGO-Virgo Gravitational-Wave Transient Catalog

Search for Gravitational Waves Associated with Gamma-Ray Bursts Detected by Fermi and Swift During the LIGO-Virgo Run O3a

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Wednesday, 02 December 2020

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