Extreme mass-ratio inspirals into bosonic stars

João Bernardo dos Santos Silva

Key information

Authors:

João Bernardo dos Santos Silva (João Bernardo dos Santos Silva)

Supervisors:

Richard Pires Brito (Richard Pires Brito)

Published in

June 24, 2025

Abstract

Massive bosonic fields can form self-gravitating solitonic structures: boson stars for scalar fields and Proca stars for vector fields. For ultralight fields, these structures can describe the cores of dark matter haloes surrounding the supermassive black holes at the center of galaxies. It has been argued that future gravitational-wave detectors might be able to probe the properties of dark matter structures. We study spherically symmetric boson and Proca stars, as well as axisymmetric Proca stars, in the Newtonian limit. Linear perturbation theory is applied to all configurations, and quasinormal modes are computed for the spherically symmetric cases. The resulting eigenfrequencies are real, indicating the presence of normal modes and the absence of instabilities in this regime. We then analyse the response of each configuration to a small compact object inspiralling towards the center of the star, calculating the total energy lost by the object and comparing it across all cases. Our results show that the response of the bosonic structure depends on the nature of the field and serves as a first step towards a fully relativistic description.