Bulk viscosity effects on dissipative tidal deformability of neutron stars

In our study, we examined the impact of the bulk viscosity of dense nuclear matter containing neutrons, protons, and electrons on the tidal deformation of neutron stars. The bulk viscosity considered in the present approach originates from the direct Urca process, which acts as a restoring mechanism for chemical equilibrium. The bulk-viscous dissipation that occurs affects the dissipative tidal deformability of binary neutron stars, especially in the late phase of inspiral, which encodes the non-equilibrium properties of neutron star matter and the equation of state. By using a phenomenological nuclear model, we employed different equations of state under various temperature values for neutrino-transparent matter and for oscillation frequencies of baryon density relevant to neutron stars; we examined the aspects of the dissipative tidal deformability so that its dependence on the equation of state could be understood better. The ability to measure the parameters that are encoded in the tidal dissipative deformability by the current terrestrial gravitational wave detectors, as well as future new-generation ones, offers an extra tool for the understanding of dense nuclear matter and its characteristics. Our findings show that, under specific conditions, such effects can be potentially measurable, posing a strong motivation for further theoretical work.