A transient gravitational-wave signal , GW150914 , was identified in the twin Advanced LIGO detectors on September 14 , 2015 at 09:50:45 UTC .
To assess the implications of this discovery , the detectors remained in operation with unchanged configurations over a period of 39 \mathrm { d } around the time of the signal .
At the detection statistic threshold corresponding to that observed for GW150914 , our search of the { 16 } ~ { } \mathrm { days } of simultaneous two-detector observational data is estimated to have a false alarm rate ( FAR ) of < { 4.9 \times 10 ^ { -6 } \mathrm { yr } ^ { -1 } } { } , yielding a p -value for GW150914 of < 2 \times 10 ^ { -7 } .
Parameter estimation followup on this trigger identifies its source as a binary black hole ( BBH ) merger with component masses ( m _ { 1 } ,m _ { 2 } ) = \left ( { 36 _ { -4 } ^ { +5 } } { } , { 29 _ { -4 } ^ { +4 } } { } \right ) \mathrm { M } _ { \odot } at redshift z = { 0.09 _ { -0.04 } ^ { +0.03 } } { } ( median and 90 % credible range ) .
Here we report on the constraints these observations place on the rate of BBH coalescences .
Considering only GW150914 , assuming that all \acp BBH in the Universe have the same masses and spins as this event , imposing a search FAR threshold of 1 per 100 years , and assuming that the BBH merger rate is constant in the comoving frame , we infer a 90 \% credible range of merger rates between { 2 } \text { - - } { 53 } \mathrm { Gpc } ^ { -3 } \mathrm { yr } ^ { -1 } ( comoving frame ) .
Incorporating all search triggers that pass a much lower threshold while accounting for the uncertainty in the astrophysical origin of each trigger , we estimate a higher rate , ranging from { 13 } \text { - - } { 600 } \mathrm { Gpc } ^ { -3 } \mathrm { yr } ^ { -1 } depending on assumptions about the BBH mass distribution .
All together , our various rate estimates fall in the conservative range { 2 } \text { - - } { 600 } \mathrm { Gpc } ^ { -3 } \mathrm { yr } ^ { -1 } .