Intermediate-mass Black Holes from High Massive-star Binary Fractions in Young Star Clusters

Abstract

Black holes formed in dense star clusters, where dynamical interactions are frequent, may have fundamentally different properties than those formed through isolated stellar evolution. Theoretical models for single star evolution predict a gap in the black hole mass spectrum from roughly $40-120M_{\odot }$ caused by (pulsational) pair-instability supernovae. Motivated by the recent LIGO/Virgo event GW190521, we investigate whether black holes with masses within or in excess of this "upper-mass gap" can be formed dynamically in young star clusters through strong interactions of massive stars in binaries. We perform a set of $N$-body simulations using the CMC cluster-dynamics code to study the effects of the high-mass binary fraction on the formation and collision histories of the most massive stars and their remnants. We find that typical young star clusters with low metallicities and high binary fractions in massive stars can form several black holes in the upper-mass gap and often form at least one intermediate-mass black hole. These results provide strong evidence that dynamical interactions in young star clusters naturally lead to the formation of more massive black hole remnants.

10 pages, 2 figures, 1 table. Accepted for publication in ApJ Letters. Comments welcome

References in corpus (14)

• Binary interaction dominates the evolution of massive stars
• GW190521: A Binary Black Hole Merger with a Total Mass of $150M_{\odot }$
• Primordial Black Holes as Dark Matter
• Pulsational Pair-Instability Supernovae
• Pulsational pair instability as an explanation for the most luminous supernovae
• The Effect of Pair-Instability Mass Loss on Black Hole Mergers
• Mind the gap: The location of the lower edge of the pair instability supernovae black hole mass gap
• Very massive stars, pair-instability supernovae and intermediate-mass black holes with the SEVN code
• The Dynamical Evolution of Stellar Black Holes in Globular Clusters
• Merging black holes in young star clusters
• The Evolution of Massive Helium Stars Including Mass Loss
• Repeated mergers and ejection of black holes within nuclear star clusters
• Generation of massive stellar black holes by rapid gas accretion in primordial dense clusters
• $N-$body dynamics of Intermediate mass-ratio inspirals in globular clusters

Cited by in corpus (3)

• Stellar-mass black holes in young massive and open stellar clusters V: comparisons with LIGO-Virgo merger rate densities
• Detection of LIGO-Virgo binary black holes in the pair-instability mass gap
• Using Binaries in Globular Clusters to Catch Sight of Intermediate-Mass Black Holes