LISA and SKAO Simulations Forecast Robust Radio Counterparts for mHz Gravitational-Wave Black Hole Binaries

The preprint employs shared binary populations evolved under hydrodynamical torques to predict coincident signals. LISA resolves the mHz inspiral while SKAO captures nHz stochastic backgrounds via pulsar timing arrays and direct radio emission from the same systems. This dual-band gravitational-wave channel arises because disc interactions excite higher-frequency harmonics that LISA registers as a stochastic foreground once the primary nHz carrier is timed by SKAO-era arrays.

Mainstream coverage emphasises sensitivity gains but overlooks how the same torque-driven perturbations produce measurable frequency shifts that break degeneracies between binary mass and environment density. The authors tested multiple flare and jet prescriptions and found detection rates vary by less than a factor of two, a result stronger than single-messenger forecasts that typically assume optimistic accretion efficiencies.

Contextual comparison with earlier LISA-only and PTA-only studies reveals that joint selection reduces false-positive rates for both instruments by anchoring sky location and chirp mass. The principal limitation remains the uncertain fraction of binaries retaining dense gas discs at sub-parsec separations; wider parameter surveys with self-consistent radiative transfer are required before robust rate predictions can be issued.

Next steps include cross-matching LISA alerts with SKAO deep fields once both facilities operate, plus targeted PTA searches for the nHz carrier once LISA stochastic signals are catalogued.