Speaker
Description
Additional fundamental fields can modify compact-binary radiation, with dipole-radiation effects entering most strongly during the early inspiral. Although binary black holes do not emit leading-order dipole radiation in many commonly studied theories, more general scenarios can endow them with effective charges or additional radiation channels. Space-ground multiband observations therefore provide a valuable opportunity for theory-agnostic tests of such effects. However, residual orbital eccentricity is also most prominent at low frequencies and can introduce important parameter degeneracies.
In this talk, I will present a Bayesian multiband analysis that simultaneously includes eccentricity and a theory-agnostic -1PN dipole-radiation correction. We find strong correlations among the dipole parameter, chirp mass, and eccentricity. Allowing for eccentricity broadens the dipole-radiation posterior, showing that neglecting it may lead to overly optimistic constraints. Building on our previous work on eccentric archival searches and ground-informed inference, we analyze a GW231123-like binary in noisy TianQin and LISA data. With one year of space-based observation and priors informed by a next-generation ground-based detector network, the dipole parameter can still be constrained to approximately $|b|\lesssim \mathcal{O}(10^{-7})$. These results demonstrate both the potential of multiband binary black holes for tests of gravity and the importance of complete waveform modeling.