GW170104

GW170104 is a gravitational-wave event detected on January 4, 2017 by the LIGO observatories. The signal was observed in both LIGO Hanford and LIGO Livingston detectors, with no confirmed electromagnetic counterpart reported. The event occurred during a period when Virgo was not in a sensitive observing mode for that sky region, so the network localization was relatively broad.

The signal originated from the merger of two black holes. The component masses are estimated to be around 31 and 20 solar masses in the source frame, yielding a final black hole of roughly 48 solar masses. The merger released a substantial amount of energy in gravitational waves, on the order of a few solar masses’ worth of energy (about 3 solar masses c^2). The source was located at a luminosity distance of approximately 880 megaparsecs, corresponding to a redshift of about 0.18.

GW170104 contributed to the expanding catalog of gravitational-wave discoveries that confirmed the population of stellar-mass black-hole binaries in the universe. The event, like other detections in this era, was used to test general relativity in the strong-field regime and to constrain properties of gravitational-wave propagation, including limits on non-GR polarizations and graviton mass. No deviations from general relativity were detected within the measurement uncertainties. The event is part of the LIGO-Virgo collaboration’s first gravitational-wave transient catalog and helped refine models of binary black-hole formation and evolution.