Rapid Merger of Binary Primordial Black Holes: an Implication for GW150914

TL;DR

This paper introduces a new mechanism for rapid merger of primordial black hole binaries through interactions with dark matter and circumbinary disks, potentially explaining gravitational wave events like GW150914.

Contribution

It presents a novel scenario combining dynamical friction, dark matter scattering, and disk interactions to explain quick binary black hole mergers.

Findings

Binary PBHs can merge faster than the universe's age due to these processes.

Estimated gravitational wave background density parameter.

Implications for formation of intermediate to supermassive black holes.

Abstract

We propose a new scenario for the evolution of a binary of primordial black holes (PBHs). We consider a dynamical friction by ambient dark matter, scattering of dark matter particles with a highly eccentric orbit besides the standard two-body relaxation process to refill the loss cone, and interaction between the binary and a circumbinary disk, assuming that PBHs do not constitute the bulk of dark matter. Binary PBHs lose the energy and angular momentum by these processes, which could be sufficiently efficient for a typical configuration. Such a binary coalesces due to the gravitational wave emission in a time scale much shorter than the age of the universe. We estimate the density parameter of the resultant gravitational wave background. Astrophysical implication concerning the formation of intermediate-mass to supermassive black holes is also discussed.