Hyperon bulk viscosity and $r$-modes of neutron stars

Abstract

We propose and apply a new parameterization of the modified chiral effective model to study rotating neutron stars with hyperon cores in the framework of the relativistic mean-field theory. The inclusion of mesonic cross couplings in the model has improved the density content of the symmetry energy slope parameters, which are in agreement with the findings from recent terrestrial experiments. The bulk viscosity of the hyperonic medium is analyzed to investigate its role in the suppression of gravitationally driven $r$-modes. The hyperonic bulk viscosity coefficient caused by non-leptonic weak interactions and the corresponding damping timescales are calculated and the $r$-mode instability windows are obtained. The present model predicts a significant reduction of the unstable region due to a more effective damping of oscillations. We find that from $\sim 10^8$ K to $\sim 10^9$ K, hyperonic bulk viscosity completely suppresses the $r$-modes leading to a stable region between the instability windows. Our analysis indicates that the instability can reduce the angular velocity of the star up to $\sim$0.3~${\Omega }_K$, where ${\Omega }_K$ is the Kepler frequency of the star.

9 pages, 9 figures; Accepted for publication in MNRAS

References in corpus (13)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• Shapiro delay measurement of a two solar mass neutron star
• A Massive Pulsar in a Compact Relativistic Binary
• GW190814: Gravitational Waves from the Coalescence of a 23 M${}_{\odot }$ Black Hole with a 2.6 M${}_{\odot }$ Compact Object
• A NICER View of PSR J0030+0451: Millisecond Pulsar Parameter Estimation
• f(R) Gravity and Chameleon Theories
• A lower bound on the maximum mass if the secondary in GW190814 was once a rapidly spinning neutron star
• Hyperon mixing and universal many-body repulsion in neutron stars
• Many-body forces in the equation of state of hyperonic matter
• Effect of hyperon-hyperon interaction on bulk viscosity and r-mode instability in neutron stars
• Bulk viscosity in neutron stars with hyperon cores
• On attributes of a Rotating Neutron star with a Hyperon core
• Nuclear symmetry energy with mesonic cross-couplings in the effective chiral model