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This study examines how chemical reactions at finite rates affect oscillation modes in neutron stars containing hyperonic matter. The researchers calculated non-leptonic weak interaction rates and incorporated them into perturbation equations, revealing that finite-rate effects produce bulk-viscous dissipation that modifies fundamental and gravity modes. They demonstrated how this viscous dissipation creates a tidal lag during binary neutron star inspirals, connecting microscopic reaction rates to observable gravitational-wave signatures.
Why it matters
This work provides a more realistic framework for interpreting gravitational-wave observations from merging neutron stars, which could help determine the composition and equation of state of ultra-dense matter. The findings are relevant for improving models used to extract astrophysical information from gravitational-wave detectors like LIGO and Virgo.
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⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
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Abstract: Tidal excitations of stellar oscillation modes during binary neutron-star inspirals offer a powerful probe of the composition of dense matter at supranuclear densities. Chemical equilibration plays a crucial, but often neglected, role in stellar perturbation calculations. If the chemical equilibration timescale is comparable to the oscillation timescale, then viscous effects can damp the modes. If the reactions are fast, some modes can completely disappear since their restoring force vanishes. Typically, these calculations, however, assume either instantaneous chemical equilibrium or no equilibration (frozen composition). Motivated by this, we investigate the effects of finite reaction rates on the oscillation spectrum of neutron stars containing hyperonic matter. We calculate the dominant non-leptonic weak interaction rates and incorporate them into the relativistic perturbation equations through a complex, frequency-dependent dynamical sound speed. We show that finite-rate effects naturally manifest as bulk-viscous dissipation, modifying the properties of both the fundamental ($f$) and gravity ($g$) modes. We further examine the impact on the tidal response by matching stellar perturbations to near-zone boundary conditions, demonstrating how viscous dissipation gives rise to a tidal lag. These results provide a consistent framework connecting microscopic reaction rates and the resulting bulk viscosity to the tidal dynamics of compact binaries, and represent a step towards incorporating viscous dissipation into gravitational-wave models of binary neutron-star inspirals.
Source: Oscillations of Dissipative Neutron Stars: The Impact of Hyperonic Reaction Rates