Date: 24.03.2026

Neha Singh (UIB,ES)

Probing the Evolution of Binary Black Holes from Population III Stars

Abstract:
To date, the LVK network of gravitational-wave (GW) detectors has identified over 300 compact binary coalescences. These detections reveal a broad spread in the binary black hole (BBH) mass distribution. The higher end (∼60 M⊙ and above) is especially intriguing astrophysically, as the formation scenarios for such high-mass black holes remain poorly understood. One potential channel for the formation of high-mass BBHs is from very massive, metal-poor (Pop III) binary stars evolving in isolation. While the possibility of Pop III remnants contributing to GW sources has been extensively considered—and may account for a significant fraction of current and future detections—there has been no direct observation of Pop III stars or their remnants to date. Strong constraints on merger rate density evolution, particularly in the era of next-generation GW detectors, will allow us to directly exclude specific formation models and constrain binary evolutionary parameters. Currently, only a handful of models for metal-free Pop III binary evolution exist. We use the population synthesis code StarTrack to generate the most up-to-date simulation families of Pop III compact binaries. This work will enable the strongest constraints yet on the evolutionary parameters of Pop III binaries using detections from next-generation GW observatories.