LIGO-Virgo-KAGRA Collaboration Announce the 200th Gravitational Wave Detection of O4!
The international gravitational wave network LVK, which is the collaboration of LIGO, Virgo and KAGRA, reported the 200th gravitational wave candidate event on March 19, 2025. The current observing run O4 started May 2023, and is ongoing now with 24 hours a day continually, while there were periods of maintenance of the instruments. The researchers of KAGRA participate observation shift 8 hours a day together with researchers in LIGO-India and LIGO-Ozgrav. Gravitational wave events are detected twice a week in average, and they have also been immediately reported to astronomers worldwide via NASA’s General Coordinates Network (GCN, https://gcn.nasa.gov) and Scalable Cyberinfrastructure to support Multi-Messenger Astrophysics (SCiMMA, https://scimma.org).
Members of the LIGO-Virgo-KAGRA collaboration around the globe are celebrating this achievement.
- Francesco Di Renzo, Postdoctoral Researcher, Institut de Physique des 2 Infinis de Lyon, Virgo collaboration: “Beyond its scientific impact for the whole astronomical community, this effort has been a powerful catalyst for [global] collaboration, fostering synergies among members who may be geographically distant or come from different research fields.”
- Keita Kawabe, Senior Scientist, LIGO Hanford Observatory, Caltech, LIGO Scientific Collaboration: “After 9.5 years of discoveries, the detection of gravitational waves is not a special occasion any more, it’s a part of our daily lives. In O4 alone, over the course of 82 weeks so far, a total of 200 significant public alerts have been handled by a team comprising hundreds of individuals affiliated with Virgo, KAGRA and LIGO. ”
- Takahiro Sawada, Associate Professor, Institute for Cosmic Ray Research, University of Tokyo, KAGRA Collaboration: “Reaching the 200th candidate from O4 is a very emotional milestone. This achievement reflects the dedication of and invaluable contributions of all collaborators across all fields within LVK. I extend my heartfelt gratitude to all collaboration members. Yet, this milestone is not an endpoint, but merely the beginning of new challenges. We are confident that many more groundbreaking discoveries await us, and we will continue this extraordinary journey alongside our esteemed colleagues.”
The 200th event, believed to be a binary black hole merger, is a milestone discovery. In three previous observing runs (O1, O2, and O3) taking place over 23 months between September 2015 and March 2020, the international gravitational wave detector network recorded 90 gravitational wave detections (catalogs of these events can be found in the Gravitational Wave Open Science Center https://gwosc.org/). This latest run, O4, has now itself spanned 23 months, and candidate detections from O4 alone now number 200!
LVK is planning to announce the results of the early part of O4 as catalog papers in coming months. The series of reports will include astrophysics of black holes and neutron stars, the tests of general relativity, the implications to cosmology and galaxies, and so on. Stay tuned for the next news.
The KAGRA detector participated in the O4 observation run together with LIGO for about one month starting on May 25, 2023. After that, operations were suspended to carry out sensitivity enhancement work. Although the detector was damaged by the Noto Peninsula Earthquake on January 1, 2024, recovery of the equipment was completed around autumn of the same year. Sensitivity enhancement work has since resumed, and preparations are underway for rejoining O4 and achieving the first gravitational wave detection with the KAGRA detector.
