Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to https://gcn.nasa.gov.
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

Gravitational Wave Network

LIGO logoVirgo logoKAGRA logo

Planned Lifetime: 2028+

End of Operations: No specific requirement

Data Archive: GW Open Science Center

LIGO, Virgo, and KAGRA comprise the advanced gravitational wave detector network. LIGO is operated by the National Science Foundation, Virgo by the European Gravitational Wave Observatory, and KAGRA by the ministry of Education, Culture, Sports, Science and Technology-Japan (MEXT). Together they detect, localize, and characterize the coalescence of compact binary mergers, continuous gravitational waves, and burst gravitational waves.

InterferometersLocationSizeJoined GW NetworkBNS Range (O4)
Laser Interferometer Gravitational-Wave Observatory (LIGO)Hanford, WA, USA Livingston, LA, USA5 km2015160-190 Mpc
Virgo Gravitational Wave Interferometer (Virgo)Pisa, Italy3 km201790-120 Mpc
Kamioka Gravitational Wave Detector (KAGRA)Kamioka-cho, Hida-city, Gifu-prefecture, Japan3 km202025-230 Mpc
LVK Observing Timeline

GCN Notice Types in GCN Classic and GCN Classic Over Kafka: Detailed Descriptions and Examples

TypeContentsLatency
LVC_EARLY_WARNINGA pre-merger alert.-1-0 minutes
LVC_PRELIMINARYFirst Notice, Timestamp Alert, location probability sky map; all automated processing.1–10 minutes
LVC_INITIALImproved SkyMap now available (human-involved processing).4–24 hours
LVC_UPDATEUltimate refined sky map (more detailed off-line processing).~1–7 days
LVC_RETRACTIONAfter human analysis/evaluation, a retraction will be issued if trigger is not astrophysical.1 hour–1 day

Common GCN Circular Types:

TypeLatencyExample
Identification of a GW trigger4-24 hoursLIGO/Virgo S191105e
Updated sky localization of a GW trigger1-7 daysLIGO/Virgo S191105e
Retraction of a GW trigger1 dayLIGO/Virgo S191117j

Predicted Annual Detection Rates for O4:

Merger ClassDetection Rates per Calendar YearArea [deg2]
Binary Neutron Star10 (0–62)33 (28–38)
Neutron Star-Black Hole1 (0–92)50 (42–58)
Binary Black Hole79 (35–168)41 (35–48)

O4 predictions from Abbott et al. 2020, LRR. Uncertainties are the 90% confidence interval, including Poisson uncertainty. This document is updated periodically for future observing runs.

Looking for U.S. government information and services? Visit USA.gov