# Dynamical Scalarization during Neutron Star Mergers in scalar-Gauss-Bonnet Theory

## TL;DR

This paper investigates how dynamical scalarization occurs during neutron star mergers in scalar-Gauss-Bonnet theory, revealing universal relations and potential for constraining the theory's parameters.

## Contribution

It introduces the concept of dynamical scalarization in neutron star mergers within scalar-Gauss-Bonnet theory and identifies universal relations to constrain theory parameters.

## Key findings

- Scalarization threshold is lower in binary systems, especially symmetric ones.
- A universal relation links critical coupling strength to neutron star compactness.
- Scalar radiation during mergers is analyzed and characterized.

## Abstract

In certain classes of the scalar-Gauss-Bonnet theory strong spacetime curvature in the vicinity of neutron stars and black holes can spontaneously trigger scalarization in the compact object if the coupling strength of the scalar field to the Gauss-Bonnet invariant exceeds a critical value. Specifying on neutron stars, this threshold depends on the mass and equation of state. The presence of a companion will further influence the required coupling strength for scalarization, and thus, a stable hair can be installed at a lower magnitude of coupling for those neutron stars as members of binaries. Focusing on binary neutron star mergers, we investigate this latter dynamically-driven scalarization, and find that the reduction in the threshold coupling strength seems to be more profound for symmetric binaries, while the threshold is only marginally reduced for rather asymmetric binaries. The associated scalar radiation is also discussed. We discover in addition a universal relation between the critical coupling strength and the stellar compactness for isolated neutron stars and perform a detailed comparison with the dynamical scalarization threshold. In synergy with such relations, one can, at least in principle, constrain the theory parameters regardless of the uncertainty in the equation of state.