GW170817A as a Hierarchical Black Hole Merger

Abstract

Despite the rapidly growing number of stellar-mass binary black hole mergers discovered through gravitational waves, the origin of these binaries is still not known. In galactic centers, black holes can be brought to each others' proximity by dynamical processes, resulting in mergers. It is also possible that black holes formed in previous mergers encounter new black holes, resulting in so-called hierarchical mergers. Hierarchical events carry signatures such as higher-than usual black hole mass and spin. Here we show that the recently reported gravitational-wave candidate, GW170817A, could be the result of such a hierarchical merger. In particular, its chirp mass $\sim 40$ M${}_{\odot }$ and effective spin of ${\chi }_{\mathrm{eff}}\sim 0.5$ are the typically expected values from hierarchical mergers within the disks of active galactic nuclei. We find that the reconstructed parameters of GW170817A strongly favor a hierarchical merger origin over having been produced by an isolated binary origin (with an Odds ratio of $>10^3$, after accounting for differences between the expected rates of hierarchical versus isolated mergers)

6 pages, 3 figures

References in corpus (5)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• Advanced Virgo: a 2nd generation interferometric gravitational wave detector
• Pulsational Pair-Instability Supernovae
• AGN Disks Harden the Mass Distribution of Stellar-mass Binary Black Hole Mergers
• Remnant mass, spin, and recoil from spin aligned black-hole binaries

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• Gravitational wave source populations: Disentangling an AGN component
• Ancestral Black Holes of Binary Merger GW190521
• Search for Black Hole Merger Families
• Synchronizing the EMRIs and IMRIs in AGN accretion disks
• Detection of LIGO-Virgo binary black holes in the pair-instability mass gap
• Dynamics of Binary System around Supermassive Black Hole
• Comparing hierarchical black hole mergers in star clusters and active galactic nuclei
• Electromagnetic signatures of white dwarf collisions in AGN discs
• Gravitational wave signals from long lasting binary-single black hole encounters