The impact of confusion noise on golden binary neutron-star events in next-generation gravitational-wave observatories*

Next-generation terrestrial gravitational-wave observatories will detect hundreds of thousands of signals from compact binary coalescences every year. These signals can last for several hours in the detectors' sensitivity band and they will be affected by multiple unresolved sources contributing to a confusion-noise background in the data. Using an information-matrix formalism, we estimate the impact of the confusion noise power spectral density in broadening the parameter estimates of a GW170817-like event. If our estimate of the confusion noise power spectral density is neglected, we find that masses, spins, and distance are biased in about half of our simulations under realistic circumstances. The sky localization, while still precise, can be biased in up to 80% of our simulations, potentially posing a problem in follow-up searches for electromagnetic counterparts.