Neutron-star mergers in scalar-tensor theories of gravity

TL;DR

This paper investigates how scalar-tensor theories of gravity alter neutron-star binary mergers, highlighting differences from General Relativity in late-inspiral and merger phases, with implications for gravitational wave detection.

Contribution

It demonstrates that neutron-star binaries exhibit significant deviations from General Relativity in scalar-tensor theories, especially due to spontaneous scalarization effects during late evolution stages.

Findings

Neutron-star binaries show marked differences from GR in late-inspiral and merger phases.

Spontaneous scalarization occurs in isolated neutron stars and affects binary dynamics.

Results are relevant for gravitational wave observations with LIGO/Virgo.

Abstract

Scalar-tensor theories of gravity are natural phenomenological alternatives to General Relativity, where the gravitational interaction is mediated by a scalar degree of freedom, besides the usual tensor gravitons. In regions of the parameter space of these theories where constraints from both solar system experiments and binary-pulsar observations are satisfied, we show that binaries of neutron stars present marked differences from General Relativity in both the late-inspiral and merger phases. In particular, phenomena related to the spontaneous scalarization of isolated neutron stars take place in the late stages of the evolution of binary systems, with important effects in the ensuing dynamics. We comment on the relevance of our results for the upcoming Advanced LIGO/Virgo detectors.