Sequential Black-Hole Mergers in Hierarchical Triples

by Felix Heinze

Friday 30 Oct 2026, 14:00 → 15:30 Europe/Berlin

Abbeanum/1- SR 102 (TPI, FSU Jena)

Two black-hole merger events with compatible first-merger remnant and second-merger component masses and overlapping spatial localizations may originate from sequential mergers in a pre-existing hierarchical black-hole triple. In this scenario, the inner binary merges first, leaving a remnant that remains bound to the tertiary and subsequently undergoes a second merger. We discuss potential hierarchical-merger pairs proposed in the literature and present a method to constrain the progenitor triple’s outer orbit by modeling the gravitational-wave-driven evolution of the remnant-tertiary binary using Peters’ equations.  Given an assumed upper bound on the recoil velocity of the first merger, the method requires only the black-hole masses, the time delay between the mergers, and the eccentricity at a reference frequency — quantities that can be inferred from the merger events themselves.

If time permits, we can also shortly discuss recently developed physics-informed machine-learning methods for solving the Hamilton constraint equation in the last part of the seminar.