Radiative viscosity of neutron stars

TL;DR

This paper investigates the non-linear effects of radiative viscosity in neutron star matter, revealing how neutrino emission and viscous dissipation vary with oscillation amplitude, impacting neutron star dynamics.

Contribution

It provides the first analysis of non-linear effects on radiative viscosity in neutron stars for both Urca processes, showing how these effects alter energy dissipation mechanisms.

Findings

Non-linear effects reduce the ratio of radiative to bulk viscosity significantly.

For small oscillations, neutrino emission dominates energy loss.

For large oscillations, bulk viscous dissipation becomes dominant.

Abstract

We study non-linear effects of radiative viscosity of $npe$ matter in neutron stars for both direct Urca process and modified Urca process, and find that non-linear effects will decrease the ratio of radiative viscosity to bulk viscosity from 1.5 to 0.5 (for direct Urca process) and 0.375 (for modified Urca process). Which means that for small oscillations of neutron star, the large fraction of oscillation energy is emitted as neutrinos; but for large enough ones, bulk viscous dissipation dominates.