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An Anonymous Coward writes:

We describe the observation of GW170104, a gravitational-wave signal produced by the coalescence of
a pair of stellar-mass black holes. The signal was measured on January 4, 2017 at 10∶11:58.6 UTC by the
twin advanced detectors of the Laser Interferometer Gravitational-Wave Observatory during their second
observing run, with a network signal-to-noise ratio of 13 and a false alarm rate less than 1 in 70 000 years.
The inferred component black hole masses are 31.2

[...]

The first observing run of the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) [1] identified two binary black hole coalescence signals with high statistical significance, GW150914 [2] andGW151226 [3], as well as a less significant candidate LVT151012 [4,5]. These discoveries ushered in a new era of observational astronomy, allowing us to investigate the astrophysics of binary black holes and test general relativity (GR) in ways that were previously inaccessible [6,7]. We now know that there is a population of binary black holes with component masses ≳25M⊙ [5,6], and that merger rates are high enough for us to expect more detections [5,8]. Advanced LIGO’s second observing run began on November 30, 2016. On January 4, 2017, a gravitational wave signal was detected with high statistical significance. Figure 1 shows a time-frequency representation of the data from the LIGO Hanford and Livingston detectors, with the signalGW170104 visible as the characteristic chirp of a binary coalescence.

https://dcc.ligo.org/LIGO-P170104/public [ligo.org]

Once again, no visual confirmation. This time possibly due to technical issues with one detector:

The event candidate was not reported by the low-latency analysis pipelines because re-tuning the calibration of the LIGO Hanford detector is not yet complete after the holiday shutdown. This resulted in a delay of over 4 hours before the candidate could be fully examined. We are confident that this is a highly significant event candidate, but the calibration issue may be affecting the initial sky maps.

https://gcn.gsfc.nasa.gov/other/G268556.gcn3 [nasa.gov]

Original Submission