LIGO-Virgo-KAGRA releases GWTC-5.0, expanding gravitational-wave catalog to 390 events

The LIGO-Virgo-KAGRA collaboration has released GWTC-5.0, adding 150 likely compact-binary merger candidates from the second half of its fourth observing run and bringing its cumulative gravitational-wave catalog to 390 transients that meet the group’s selection criteria. The update marks a milestone for a field that, just a decade after its first detection, is moving from occasional discoveries to a sample large enough for population-scale astronomy.

That larger catalog is what makes the new release important beyond the raw count. With nearly 400 signals now in hand, researchers can better study how black holes are distributed by mass and spin, compare merger rates across cosmic time, and push harder on tests of Albert Einstein’s general theory of relativity. “Nearly 400 gravitational-wave events accumulated in our catalog have ushered us into a new era of statistical astronomy—where this growing collection of detected signals enables population studies and tests of general relativity with unprecedented precision,” Leo Tsukada of the University of Nevada, Las Vegas, said in a LIGO news release.

The results are described in a paper titled “GWTC-5.0: Observations from the Second Part of the Fourth LIGO-Virgo-KAGRA Observing Run and Updates to the Gravitational-Wave Transient Catalog,” submitted to arXiv on May 26. The release covers O4b, the second part of the fourth observing run, spanning April 10, 2024, to Jan. 28, 2025, along with a preceding engineering run. The 150 new candidates were identified by at least one search method, had at least a 50% probability of being astrophysical in origin and were not vetoed during event validation. Of those, 103 had detailed source-property measurements because their false-alarm rate was below one per year.

In this release, the O4b candidates are all consistent with binary black hole mergers. The paper reports no binary neutron star or neutron star-black hole signals in this batch. Median inferred component masses across the catalog span from 5.14 times the mass of the sun for GW241109_115924 to 70 solar masses for GW241116_151753, underscoring the wide range of black hole systems now turning up in the data.

A few detections stand out. One, GW250114_082203, reached a network signal-to-noise ratio above 70; the LIGO news release put it at 76.9 and said the signal arrived at Earth on Jan. 14, 2025. LVK said a signal that loud allows especially precise measurements of the source and unusually stringent tests of general relativity. Another, GW240615, was described by LIGO as the best-localized gravitational-wave event yet, pinned to a sky area of about 6 square degrees thanks to coincident observations by the LIGO detectors in Washington state and Louisiana and Virgo in Italy. “We knew that Virgo’s contribution would be decisive in improving the localization of observed gravitational wave sources… and we are proud of the outstanding work carried out by the team responsible for commissioning the detector, which has been rewarded by this record-setting result,” said Marie Anne Bizouard, spokesperson for the Virgo Collaboration.

The bigger sample is also feeding into cosmology. According to the LIGO news release, the expanded catalog enabled an updated gravitational-wave-based estimate of the Hubble constant, a measure of how fast the universe is expanding, with about 25% better precision than the collaboration’s previous result. “The Hubble constant tells us how fast the Universe is expanding and how old it is… Using a new set of gravitational-wave sources, we obtain an independent measurement of the Hubble constant with about 25% improved precision over previous results,” said Hsin-Yu Chen of the University of Texas at Austin.

LIGO operates two U.S. observatories, in Hanford, Washington, and Livingston, Louisiana; Virgo is based in Italy; and KAGRA is in Japan. Together they form the LVK collaboration, which publishes the gravitational-wave transient catalogs. GWTC-4.0, covering the first half of the fourth observing run, added 128 candidates and brought the catalog to 218. GWTC-5.0 extends that tally to 390. One note on the counting: The formal paper reports 150 O4b candidates, while a LIGO news release used slightly different wording and said 161 new gravitational-wave events were detected during O4b.