New class of quasinormal modes of neutron stars in scalar-tensor gravity

TL;DR

This paper identifies new quasinormal modes in neutron stars caused by scalar-tensor gravity, which could be detected through electromagnetic and gravitational wave observations, offering a novel way to test gravity theories.

Contribution

It demonstrates the existence of new neutron star oscillation modes specific to scalar-tensor gravity, distinct from general relativity, and discusses their potential detectability.

Findings

New families of neutron star modes identified in scalar-tensor theories.

Modes are sufficiently distinct to be detected in frequency space.

Potential for electromagnetic and gravitational wave detection of these modes.

Abstract

Detection of the characteristic spectrum of pulsating neutron stars can be a powerful tool not only to probe the nuclear equation of state, but also to test modifications to general relativity. However, the shift in the oscillation spectrum induced by modified theories of gravity is often small and degenerate with our ignorance of the equation of state. In this Letter, we show that the coupling to additional degrees of freedom present in modified theories of gravity can give rise to new families of modes, with no counterpart in general relativity, which could be sufficiently well resolved in frequency space as to allow for a clear detection. We present a realization of this idea by performing a thorough study of radial oscillations of neutron stars in massless scalar-tensor theories of gravity. We anticipate astrophysical scenarios where the presence of this class of quasinormal modes could be probed with electromagnetic and gravitational wave measurements.