Black hole mergers from quadruples

Abstract

With the hundreds of merging binary black hole (BH) signals expected to be detected by LIGO/Virgo, LISA and other instruments in the next few years, the modeling of astrophysical channels that lead to the formation of compact-object binaries has become of fundamental importance. In this paper, we carry out a systematic statistical study of quadruple BHs consisting of two binaries in orbit around their center of mass, by means of high-precision direct N -body simulations including Post-Newtonian (PN) terms up to 2.5PN order. We found that most merging systems have high initial inclinations and the distributions peak at ∼ 90 • as for triples, but with a more prominent broad distribution tail. We show that BHs merging through this channel have a significant eccentricity in the LIGO band, typically much larger than BHs merging in isolated binaries and in binaries ejected from star clusters, but comparable to that of merging binaries formed via the GW capture scenario in clusters, mergers in hierarchical triples, or BH binaries orbiting intermediate-mass black holes in star clusters. We show that the merger fraction can be up to ∼ 3-4× higher for quadruples than for triples. Thus even if the number of quadruples is 20%-25% of the number of triples, the quadruple scenario can represent an important contribution to the events observed by LIGO/VIRGO.

Modeling Dense Star Clusters in the Milky Way and Beyond with the CMC Cluster Catalog

“…However, as noted by (e.g., Gnedin et al 2014;Fragione et al 2018a), there likely existed a significant population of clusters which did not survive to the present. The remnants of these disrupted clusters may contribute significantly to the BBH merger rate (e.g., Rodriguez & Loeb 2018;Fragione & Kocsis 2018). Furthermore, in this study we have considered only GCs, however previous analyses (e.g., Ziosi et al 2014;Banerjee 2018;Di Carlo et al 2019) have shown that lower-mass open clusters may also contribute to the BBH merger rate.…”

Formation and Merging of Mass Gap Black Holes in Gravitational-wave Merger Events from Wide Hierarchical Quadruple Systems

“…In this study we did not model an ensemble of quadruple systems and follow their evolution by direct numerical integration as is done in previous studies (e.g., Fragione & Kocsis 2019). Our goal was to sketch out a new possible path for the formation of a mass-gap BH in merging BBH systems without relying on specific supernovae mechanism to explain their existence.…”

A census of main-sequence interactions in the Multiple Star Catalogue

“…For quadruples, which occur in two long-term stable configurations ('2+2': two binaries orbiting each other, and '3+1': a triple orbited by a fourth body). The secular dynamical evolution of quadruples has been studied by a number of authors (Pejcha et al 2013;Hamers et al 2015;Vokrouhlický 2016;Hamers & Lai 2017;Fang et al 2018;Grishin et al 2018;Liu & Lai 2019;Fragione & Kocsis 2019), who have generally found that the efficiency to attain high eccentricities in quadruples is higher compared to equivalent triples, i.e., if two stars would be replaced by a single star. Also, when combined with stellar evolution, quadruples can give rise to a wide range of outcomes (Hamers 2018b).…”