Search for Sub-Solar Mass Binaries with Einstein Telescope and Cosmic Explorer

A possible detection of sub-solar mass ultra-compact objects would lead to new perspectives on the existence of black holes that are not of astrophysical origin and/or pertain to formation scenarios of exotic ultra-compact objects. Both possibilities open new perspectives for better understanding of our universe. In this work, we investigate the significance of detection of sub-solar mass binaries with components mass in the range: 10(-2)M(circle dot) up to 1M(circle dot), within the expected sensitivity of the ground-based gravitational waves detectors of third generation, viz., the Einstein Telescope (ET) and the Cosmic Explorer (CE). Assuming a minimum of amplitude signal-to-noise ratio for detection, viz., rho = 8, we find that the maximum horizon distances for an ultra-compact binary system with components mass 10(-2) M-circle dot and 1M(circle dot) are 40 Mpc and 1.89 Gpc, respectively, for ET, and 125 Mpc and 5.8 Gpc, respectively, for CE. Other cases are also presented in the text. We derive the merger rate and discuss consequences on the abundances of primordial black hole (PBH), f(PBH). Considering the entire mass range [10(-2)-1]M-circle dot, we find f(PBH) < 0.70 ( <0.06) for ET (CE), respectively.

Automated summary

This article investigates the significance of sub-solar mass binary detection and finds that the potential discovery of ultra-compact objects will provide new perspectives on the existence of non-astrophysical black holes and the formation of exotic ultra-compact objects. By simulating the detection, the article derives the merger rate of the sub-solar mass binaries and discusses its consequences on the abundances of primordial black holes.