Gravitational wave asteroseismology of neutron and strange stars in $R^2$ gravity

TL;DR

This paper investigates how $R^2$ gravity affects neutron and strange star oscillations, finding small deviations from general relativity that are unlikely to be observable soon, but still useful for estimating star parameters.

Contribution

It analyzes nonradial $f$-mode oscillations in $R^2$ gravity and assesses their impact on gravitational wave asteroseismology relations, highlighting their robustness and limited deviations from GR.

Findings

Deviations from GR are up to 10% in $R^2$ gravity.

Asteroseismology relations are largely equation of state independent.

Relations are insensitive to the gravitational theory, aiding robust parameter estimation.

Abstract

We study the oscillations of neutron and strange stars in $R^2$ gravity. More precisely the nonradial $f$-modes are examined and the differences with pure general relativity are investigated. Using these results we build several gravitational wave asteroseismology relations. Our goal is to determine up to what extend these relations are equation of state independent and whether they deviate enough from general relativity in order to produce an observable effect. The results show that the differences coming from $R^2$ gravity are up to 10\% and that will be difficult to be observed in the near future. On the other hand the small deviations in some of the asteroseismology relations show that they are not only equation of state independent, but they are also quite insensitive to the gravitational theory. That is why solving the inverse problem can give us quite robust estimates of the neutron star parameters.