Late-time signals from binary black hole mergers

Abstract

Late-time tails emitted by binary black holes mergers contain invaluable information on the spacetime’s asymptotic structure. Perturbative numerical simulations of extreme mass-ratio mergers have revealed that these tails are enhanced by several orders of magnitude with the progenitors’ binary eccentricity. This amplification has the potential to bring tails within the realm of observation and shows that this effect carries significant astrophysical implications, other than fundamental physics content.   I will present an analytical perturbative model that accurately predicts the numerically observed tail and explains its enhancement with the progenitors' binary eccentricity. The model is an integral over the system's entire history, showing how the post-ringdown tail is inherited from the non-circular inspiral in a non-local fashion. I will prove the tail to be a superposition of many power-laws, with each term's excitation coefficient depending on the specific inspiral history. A single power law is recovered only in the limit of asymptotically late times, consistent with Price's results and the classical soft-graviton theorem. Finally, I will introduce a robust framework for extracting tails in fully non-linear simulations of equal masses mergers. I will present results for late-time tails emitted by these systems and discuss their phenomenology.