Results
LIGO, Virgo and KAGRA observed 'second generation' black holes for the first time
October 29, 2025
Gravitational Waves GroupResearchers from the Institut de Física d’Altes Energies (IFAE), through its Gravitational Waves group, participate in the LIGO–Virgo–KAGRA collaboration that has reported the first observational evidence of candidate second-generation black holes. The analysis of two gravitational-wave signals reveals binary systems with unusual mass ratios and spin configurations, opening a new window on black-hole formation in dense astrophysical environments.
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.
Gravitational Waves
Spain strengthens its participation in major gravitational-wave infrastructures
December 10, 2025
The Spanish Ministry of Science, Innovation and Universities has allocated new funding to Spain’s participation in major international gravitational-wave infrastructures, with the Institut de Física d’Altes Energies (IFAE) designated as the institution through which these contributions will be channelled.
Results
LIGO–Virgo–KAGRA complete their richest gravitational-wave observation run to date
November 18, 2025
The LIGO–Virgo–KAGRA (LVK) Collaboration has announced the completion of O4, the most productive gravitational-wave observation run so far, yielding an unprecedented number of candidate events and high-quality data for the scientific community.