Public Thesis Defense of Antoine Depasse - IRMP

Searching for annihilation signals from clouds of vector bosons around black holes in X-ray binary systems by Antoine Depasse -

Lundi 12 octobre 2026 à 10h45 - Auditoire CYCL01 - Bâtiment de Hemptinne - Chemin du Cyclotron, 2 - 1348 Louvain-la-Neuve -

Since the first detection of a gravitational wave in 2015, gravitational astronomy has grown rapidly. On one hand, the catalogue of observed gravitational waves from compact-object mergers has exploded, with nearly 400 confirmed detections to date. On the other side, searches for signals with different morphologies have reached unprecedented sensitivities, probing ever deeper into the noise background.  Yet gravitational waves offer a much broader window on the universe. Because gravity couples to all forms of energy, gravitational wave astronomy is also open to more exotic phenomena, inaccessible to any electromagnetic observation. One of the most striking possibilities is using gravitational waves to search for new particles beyond the standard model of particle physics.  Ultralight bosons are a well-motivated extension of the standard model. They arise naturally in solutions to the strong CP problem and are predicted in abundance by string theory compactifications. Additionally, ultralight bosons are promising dark matter candidates. If they exist, such particles can interact gravitationally with astrophysical black holes through the so-called superradiant instability. Via this process, a rotating black hole spontaneously sheds rotational energy into a growing population of bosons, which accumulate into a macroscopic cloud surrounding the black hole. The resulting boson cloud slowly dissipates by emitting gravitational waves that could fall within the LIGO-Virgo-KAGRA sensitivity band depending on the boson mass.
In this thesis, I explore the potential of searching for boson cloud signals emitted from nearby galactic black holes. I then develop a dedicated method to search for such signals emitted from clouds of vector (spin-1) bosons. Finally, I apply this method to the promising system Cygnus X-1 using data from the O4a run of the LIGO-Virgo-KAGRA collaborations. 

Jury members :

Prof. Giacomo Bruno (UCLouvain) (Supervisor)
Prof. Paola Leaci (Sapienza Univ. di Roma, It.) (Supervisor)
Dr. Andrea Giammanco (UCLouvain) (Chairperson)
Prof. Christophe Ringeval (UCLouvain) (Secretary)
Prof. Cristiano Palomba (Sapienza Univ. di Roma, It.)
Prof. David Keitel (UIB, Spain)

Pay attention : the public defense of Antoine Depasse will also take place in the form of a videoconference