Speaker
Description
Neutron stars with admixed dark matter enable new possibilities in the description of unusal mass and radius measurements, such as e.g. HESS J1731-347. We are including bosonic, self-interacting dark matter with a sufficiently stiff self-interaction potential in the form of $V \propto \phi^n$ and find that these neutron stars become ultra-compact ($C \geq 1/3$). They are compact enough to have a stable photon orbit at their surface or even above, a property that is otherwise exclusively attributed to black holes or hypothetical boson stars. These ultra-compact neutron stars are characterized by small radii of the ordinary matter ($R < 7$ km) and masses of approximately $1.5 \, M_\odot$. We furthermore study the stability of these configurations by investigating the onset of unstable radial modes.
