CGCA Seminar – Debatri Chattopadhyay

Neutron Star–Black Hole Binaries: Predictions and Observations

Debatri Chattopadhyay
Northwestern University

Neutron star–black hole (NS–BH) binaries have emerged as key targets for multi-messenger astrophysics following the first gravitational wave detections of such systems. In this talk, I present population synthesis predictions for the Galactic NS–BH population, models that interpret the first observed mergers, and forecasts for future radio, gravitational-wave, and electromagnetic discoveries. Using binary evolution simulations, we predict tens – hundreds of NS–BH systems in the Milky Way, albeit very few of which should be detectable as pulsar–black hole binaries with next-generation radio facilities and as low-frequency gravitational-wave sources. Modelling of the first NS–BH merger events indicates consistency with low-metallicity progenitors and low black hole natal spins, implying that most mergers may produce weak or absent electromagnetic counterparts. I further show how upcoming surveys and detectors will enable joint radio and gravitational wave observations, and how kilonova searches can constrain neutron star structure in a subset of systems. These results place NS–BH binaries in a broader context of neutron star binary evolution and highlight their role as laboratories for testing compact object formation, binary evolution, and multi-messenger astrophysics in the coming decade.