Massive Stars and Heavy Black Holes in the Era of LISA
Massive stars are the progenitors of black holes—some of the most powerful sources of gravitational waves that LISA will observe.
At Armagh Observatory and Planetarium, our group investigates the formation and fate of the most massive stars in the Universe, particularly in low-metallicity environments where their evolution leads to the formation of heavy black holes (≳30 M☉).
These stellar-origin black holes are key targets for LISA.
A crucial focus of our work is understanding how black hole masses have evolved over cosmic time. As shown in the figure, the upper mass limit for black holes is predicted to shift: at early times in the Universe, conditions may allow for the formation of heavy black holes, up to 93 M☉.
In contrast, in the present-day Universe, higher metallicity and stronger stellar winds cause the most massive stars to shed their outer layers.
This results in a sharp decline in the black hole mass ceiling over Cosmic time.
Our group uses stellar wind and evolution codes to understand this time-dependent behaviour (Vink et al. 2021; Winch et al. 2024; 2025).
By modeling how stellar mass loss, interior physics, and pair-instability supernovae affect black hole birth masses, we help predict the kinds of sources LISA will detect across cosmic epochs.
LISA’s sensitivity to high-mass stellar black hole mergers, particularly those formed in low-metallicity, early-Universe environments, provides a powerful observational test of these models. We aim to connect the evolution of massive stars with the gravitational wave signals LISA will observe—probing the stellar physics encoded in black hole masses, merger rates, and spins.