1 Jun 2017 — The LIGO Scientific Collaboration and the Virgo collaboration confirmed a third gravitational wave event in data from the Advanced LIGO detectors in Livingston, Louisiana, and Hanford, Washington, USA.
The detected waves—observed on January 4th, 2017 at 10:11:58.6 UTC (5:12AM EST) —were produced by a binary black hole system. Stellar-mass black holes with 31.2 and 19.4 solar masses merged to produce a spinning black hole of 48.7 solar masses. The detected signal is completely consistent with the predictions of general relativity.
Press release at LIGO Lab site [ pdf version].
More information can be found at the ligo.org detection page for GW170104 and the LIGO Lab page for GW170104.