Tidal deformability of fermion-boson stars: Neutron stars admixed with ultralight dark matter
Robin Fynn Diedrichs, Niklas Becker, Cédric Jockel, Jan-Erik Christian, Laura Sagunski, Jürgen Schaffner–Bielich
Abstract
In this work, we investigate the tidal deformability of a neutron star admixed with dark matter, modeled as a massive, self-interacting, complex scalar field. We derive the equations to compute the tidal deformability of the full Einstein-Hilbert-Klein-Gordon system self-consistently, and we probe the influence of the scalar field mass and self-interaction strength on the total mass and tidal properties of the combined system. We find that dark matter corelike configurations lead to more compact objects with smaller tidal deformability, and dark matter cloudlike configurations lead to larger tidal deformability. Electromagnetic observations of certain cloudlike configurations would appear to violate the Buchdahl limit. The self-interaction strength is found to have a significant effect on both mass and tidal deformability. We discuss observational constraints and the connection to anomalous detections. We also investigate how this model compares to those with an effective bosonic equation of state and find the interaction strength where they converge sufficiently.