Postdoctoral Researcher · ISTA

David
O'Neill

Supermassive black hole binaries do not merge in vacuum. They are embedded in the dense environments of galactic centers, exchanging energy and momentum with the surrounding stars and gas until they spiral together in a gravitational wave-driven merger. Those waves carry the imprint of the environment that shaped them — a signal the upcoming Laser Interferometer Space Antenna (LISA) will detect directly. My research predicts these fingerprints and the physical processes behind them.

Institute of Science and Technology Austria
Haiman Group · Klosterneuburg

Research

Circumbinary disk simulations

Polar Circumbinary Disks

Three-dimensional polar-aligned disk. A circumbinary disk settled into a polar configuration, orbiting perpendicular to the binary plane. Shown in three orthogonal projections.

Circumbinary disk simulations

Retrograde Circumbinary Disks

Left: retrograde and prograde disks side by side, showing the cleared cavity of the prograde case against the direct intrabinary flow of the retrograde one. Right: a retrograde disk around an eccentric binary, with the shocked bridge structure between the black holes.

Linear perturbation theory

Dynamical Friction

Density response of a gaseous medium to a moving perturber. These play as you scroll.

Eccentric binaries

Subsonic The density wake generated by a circular, subsonic binary moving through a gaseous medium.

Transonic The density wake generated by an eccentric, transonic binary moving through a gaseous medium.

Supersonic The density wake generated by an eccentric, supersonic binary moving through a gaseous medium.

Hyperbolic encounters

Extracted wake A supersonic hyperbolic encounter where both perturbers "escape" the density wake generated during the pericenter approach.

Hyperbolic passage A supersonic hyperbolic encounter where the Mach cone "engulfs" the two perturbers after pericenter

Asymptotic regime A transonic hyperbolic encounter, where the acceleration near pericenter causes the perturbers to cross the sound barrier.

Publications

Full list on NASA ADS and ORCID.

2026

Dynamics and detectability of long-lived non-accretion phases for massive black hole binaries in cold, thermally regulating disks

C. Tiede, D. O'Neill, D. J. D'Orazio, et al.

arXiv:2606.04082

arXiv

2025

Gravitational Wave Decoupling in Retrograde Circumbinary Disks

D. O'Neill, C. Tiede, D. J. D'Orazio, Z. Haiman, A. MacFadyen

ApJ 993, 206 · doi:10.3847/1538-4357/ae0ca8

arXiv DOI

About

I'm a postdoctoral researcher at the Institute of Science and Technology Austria, working with Zoltán Haiman on circumbinary disk dynamics and gravitational wave source modelling.

I completed my PhD at the Niels Bohr Institute, University of Copenhagen, with earlier study at NUI Maynooth. My work sits at the intersection between computational and analytical hydrodynamics with gravitational wave astrophysics, with the aim of predicting the dynamics and signatures of black hole binary mergers.

Contact

david.oneill@ist.ac.at

Institution

ISTA
Am Campus 1
3400 Klosterneuburg, Austria

Profiles

ORCID · ADS · GitHub

Group

Haiman Group at ISTA