  On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser
Interferometer Gravitational-wave Observatory (LIGO) simultaneously observed
the binary black hole merger GW150914. We report the results of a
matched-filter search using relativistic models of compact-object binaries that
recovered GW150914 as the most significant event during the coincident
observations between the two LIGO detectors from September 12 to October 20,
2015. GW150914 was observed with a matched filter signal-to-noise ratio of 24
and a false alarm rate estimated to be less than 1 event per 203 000 years,
equivalent to a significance greater than 5.1 {\sigma}.
