This result is part of the scientific programme of the Institut de Física d’Altes Energies (IFAE) Gravitational Waves group, which participates in the LIGO–Virgo–KAGRA collaboration and contributes to the analysis and interpretation of gravitational-wave observations of compact-object mergers.

Detailed studies of the mass asymmetry and spin orientations show that, in both events, the more massive black hole dominates the system and exhibits spin configurations that are difficult to reconcile with standard isolated stellar-evolution scenarios. These characteristics suggest that at least one of the components may be the product of a previous merger, giving rise to what is known as a second-generation black hole.

If confirmed, these observations would constitute the first direct detection of hierarchical black-hole mergers through gravitational waves. The result provides new insights into the formation and evolution of black holes in dense astrophysical environments, such as stellar clusters, and offers a new testing ground for gravitational physics in extreme regimes.

IFAE researchers M. Andrés-Carcasona, G. Caneva, Mario Martínez and Ll. M. Mir are authors of the paper.

“GW241011 and GW241110: Exploring Binary Formation and Fundamental Physics with Asymmetric, High-Spin Black Hole Coalescences”, published on October 28 in The Astrophysical Journal Letters