Excitation of Neutron Star Oscillations by an Orbiting Particle

TL;DR

This study numerically investigates how particles orbiting neutron stars can excite gravitational waves, revealing that ultra-relativistic speeds are necessary for significant $w$-mode excitation, with implications for gravitational wave detection.

Contribution

It provides the first detailed numerical analysis of $w$-mode excitation in neutron stars due to orbiting particles under realistic conditions.

Findings

$w$-modes are rarely excited at realistic orbital speeds.

Significant $w$-mode contribution occurs only at speeds ≥ 0.9c.

Initial configuration setup critically affects excitation results.

Abstract

The excitation of neutron stars is expected to be an important source of gravitational radiation. Of fundamental importance is then to investigate mechanisms that trigger oscillations in neutron stars in order to characterize the emitted radiation. We present results from a numerical study of the even-parity gravitational radiation generated from a particle orbiting a neutron star. We focus our investigation on those conditions on the orbital parameters that favor the excitation of $w$-modes. We find that, for astrophysically realistic conditions, there is practically no $w$-mode contribution to the emitted radiation. Only for particles with ultra-relativistic orbital speeds $\ge 0.9c$, the $w$-mode does significantly contribute to the total emitted gravitational energy. We also stress the importance of setting consistent initial configurations.