Constraints on primordial black holes from the first part of LIGO-Virgo-KAGRA fourth observing run

Abstract

We analyze PBH populations using state-of-the-art modeling of PBH binaries, deriving the strongest bounds on PBH abundance in the $0.6-100 M_\odot$ range from LIGO-Virgo-KAGRA O4a data and demonstrating sensitivity in the $10^{-4}-10^4 M_\odot$ range. The constraints are dominated by resolvable PBH mergers, while the associated gravitational wave background provides complementary but weaker limits. Allowing PBHs to account for a subset of the cataloged events slightly relaxes these bounds. However, a joint fit with astrophysical black holes shows no compelling evidence for a PBH contribution.