Shell sources as a probe of relativistic effects in neutron star models

TL;DR

This paper introduces a shell perturbation method to study fluid motions in relativistic neutron star models, comparing relativistic and Newtonian results for gravitational wave generation, and finds relativistic effects are generally negligible except on very short timescales.

Contribution

It presents a novel shell perturbation approach that isolates radiation and allows flexible perturbation timing in relativistic stellar models.

Findings

Relativistic effects are minor in gravitational wave emission for most scenarios.

The shell method effectively separates radiation from fluid motions.

Relativistic and Newtonian results agree closely except on very short timescales.

Abstract

A perturbing shell is introduced as a device for studying the excitation of fluid motions in relativistic stellar models. We show that this approach allows a reasonably clean separation of radiation from the shell and from fluid motions in the star, and provides broad flexibility in the location and timescale of perturbations driving the fluid motions. With this model we compare the relativistic and Newtonian results for the generation of even parity gravitational waves from constant density models. Our results suggest that relativistic effects will not be important in computations of the gravitational emission except possibly in the case of excitation of the neutron star on very short time scales.