Characterization of the neutron star–black hole mass spectrum

Characterize the mass spectrum of neutron star–black hole binaries, including the distribution of component masses and any salient spectral features, to enable their inclusion in spectral siren cosmology analyses without incurring population-model biases.

Background

The spectral siren approach infers cosmological parameters by tracking redshift-induced shifts in the population mass spectrum across redshifts. Accurate population models are therefore essential to avoid cosmology–population degeneracies.

The authors exclude neutron star–black hole systems from their spectral siren analysis because the underlying mass spectrum is still largely unknown. Determining this spectrum would allow these sources to be incorporated and strengthen cosmological inference.