We report the detection of new binary black hole merger events in the publicly available data from the second observing run of advanced LIGO and advanced Virgo (O2). The mergers were discovered using the new search pipeline described in Venumadhav et al.[1], and are above the detection thresholds as defined in Abbott et al. [2]. Three of the mergers (GW170121, GW170304, GW170727) have inferred probabilities of being of astrophysical origin pastro > 0.98. The remaining three (GW170425, GW170202, GW170403) are less certain, with pastro ranging from 0.5 to 0.8. The newly found mergers largely share the statistical properties of previously reported events, with the exception of GW170403, the least secure event, which has a highly negative effective spin parameter χ eff . The most secure new event, GW170121 (pastro > 0.99), is also notable due to its inferred negative value of χ eff , which is inconsistent with being positive at the ≈ 95.8% confidence level. The new mergers nearly double the sample of gravitational wave events reported from O2, and present a substantial opportunity to explore the statistics of the binary black hole population in the Universe. The number of detected events is not surprising since we estimate that the detection volume of our pipeline is nearly twice that of other pipelines. The increase in volume is larger when the constituent detectors of the network have very different sensitivities, as is likely to be the case in current and future runs.

We report a new binary black hole merger in the publicly available LIGO First Observing Run (O1) data release. The event has a false alarm rate of one per six years in the detector-frame chirp-mass range M det ∈ [20, 40]M in a new independent analysis pipeline that we developed. Our best estimate of the probability that the event is of astrophysical origin is Pastro ∼ 0.71 . The estimated physical parameters of the event indicate that it is the merger of two massive black holes, M det = 31 +2 −3 M with an effective spin parameter, χ eff = 0.81 +0.15 −0.21 , making this the most highly spinning merger reported to date. It is also among the two highest redshift mergers observed so far. The high aligned spin of the merger supports the hypothesis that merging binary black holes can be created by binary stellar evolution.

In this paper, we report on the construction of a new and independent pipeline for analyzing the public data from the first observing run of advanced LIGO for mergers of compact binary systems. The pipeline incorporates different techniques and makes independent implementation choices in all its stages including the search design, the method to construct template banks, the automatic routines to detect bad data segments ("glitches") and to insulate good data from them, the procedure to account for the non-stationary nature of the detector noise, the signal-quality vetoes at the singledetector level and the methods to combine results from multiple detectors. Our pipeline enabled us to identify a new binary black-hole merger GW151216 in the public LIGO data. This paper serves as a bird's eye view of the pipeline's important stages. Full details and derivations underlying the various stages will appear in accompanying papers.

We reanalyse the LIGO-Virgo strain data of the 10 binary black hole mergers reported to date and compute the likelihood function in terms of chirp mass, mass ratio and effective spin. We discuss the strong degeneracy between mass ratio and spin for the three lighter events. We use this likelihood and an estimate of the horizon volume as a function of intrinsic parameters to constrain the properties of the population of merging binary black holes. The data disfavour large spins. Typical spins are constrained to a 0.4, even if the underlying population has randomly-oriented spins. For aligned spins the constraints are tighter, with typical spins required to be around a ∼ 0.1 and have comparable dispersion. We detect no statistically significant tendency towards a positive average spin in the direction of the orbital angular momentum. We put an upper limit on the fraction of systems where the secondary could have been tidally locked prior to the formation of the black holes (corresponding to merger times shorter than 10 8 years) f 0.3. Four events are consistent with having a maximally-spinning secondary, although one only marginally. We confirm previous findings that there is a hint of a cutoff at high mass. The data favour distributions of mass ratios with an average q 0.7.

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