Search technique to observe precessing compact binary mergers in the advanced detector era

Gravitational-wave signals from compact binary coalescences are most effectively identified by matched filter searches. These searches match the data against a pregenerated bank of gravitational-wave templates. Currently, all modeled gravitational-wave searches use templates that restrict the component spins to be aligned (or antialigned) with the orbital angular momentum. This means that they are less sensitive to gravitational-wave signals from precessing binaries, implying that a significant fraction of signals may remain undetected. In this work, we introduce a matched filter search that is sensitive to signals generated from precessing binaries. We take advantage of the fact that a gravitational-wave signal from a precessing binary can be decomposed into a power series of five harmonics. This allows us to create a generic-spin template bank that is only similar to 3 times larger than existing aligned-spin banks. Our new search shows a similar to 100 % increase in sensitive volume for neutron star black hole binaries with total mass larger than 17.5 M-circle dot and in-plane spins >0.67 , and improves sensitivity by similar to 60 % on average across the full generic spin neutron-star black-hole parameter space. In addition, our generic spin search performs as well as existing aligned-spin searches for neutron star black hole signals with insignificant in-plane spins. We anticipate that this improved technique will identify significantly more gravitational-wave signals and help shed light on the unknown spin distribution of binaries in the Universe.