The astrophysical odds of GW151216

The gravitational-wave candidate GW151216 is a proposed binary black hole event from the first observing run of the Advanced LIGO detectors. Not identified as a bona fide signal by the LIGO-Virgo collaboration, there is disagreement as to its authenticity, which is quantified by p(astro), the probability that the event is astrophysical in origin. Previous estimates of p(astro) from different groups range from 0.18 to 0.71, making it unclear whether this event should be included in population analyses, which typically require p(astro) > 0.5. Whether GW151216 is an astrophysical signal or not has implications for the population properties of stellar-mass black holes and hence the evolution of massive stars. Using the astrophysical odds, a Bayesian method that uses the signal coherence between detectors and a parametrized model of non-astrophysical detector noise, we find that p(astro) = 0.03, suggesting that GW151216 is unlikely to be a genuine signal. We also analyse GW150914 (the first gravitational-wave detection) and GW151012 (initially considered to be an ambiguous detection) and find p(astro) values of 1 and 0.997, respectively. We argue that the astrophysical odds presented here improve upon traditional methods for distinguishing signals from noise.