New binary black hole mergers in the LIGO-Virgo O3b data

We report the detection of six new candidate binary black hole (BBH) merger signals in the publicly released data from the second half of the third observing run (O3b) of advanced LIGO and advanced Virgo. The LIGO-Virgo-KAGRA (LVK) Collaboration reported 35 compact binary coalescences in their analysis of the O3b data [Phys. Rev. X 13, 041039 (2023).PRXHAE2160-330810.1103/PhysRevX.13.041039], with 30 BBH mergers having coincidence in the Hanford and Livingston detectors. We confirm 17 of these for a total of 23 detections in our analysis of the Hanford-Livingston coincident O3b data. We identify candidates using a search pipeline employing aligned-spin quadrupole-only waveforms. Our pipeline is similar to the one used in our O3a coincident analysis [Phys. Rev. D 106, 043009 (2022).PRVDAQ2470-001010.1103/PhysRevD.106.043009], except for a few improvements in the veto procedure and the ranking statistic, and we continue to use an astrophysical probability of one half as our detection threshold, following the approach of the LVK catalogs. Most of the new candidates reported in this work are placed in the upper/lower-mass gap of the black hole mass distribution. We also identify a possible neutron star-black hole merger. We expect these events to help inform the black hole mass and spin distributions inferred in a full population analysis.