Core collapse in massive scalar-tensor gravity

TL;DR

This paper systematically studies gravitational-wave signals from stellar collapse in massive scalar-tensor gravity, classifying outcomes and identifying conditions for detectable signals in ground-based detectors.

Contribution

It introduces a simple classification scheme for collapse outcomes and maps the parameter space to predict gravitational-wave detectability.

Findings

Three main collapse outcomes identified: weakly scalarized neutron star, strongly scalarized neutron star, black hole.

A sharp boundary in parameter space separates detectable from undetectable gravitational-wave signals.

Strong signals may be observed with current ground-based gravitational-wave detectors.

Abstract

This paper provides an extended exploration of the inverse-chirp gravitational-wave signals from stellar collapse in massive scalar-tensor gravity reported in [Phys. Rev. Lett. {\bf 119}, 201103]. We systematically explore the parameter space that characterizes the progenitor stars, the equation of state and the scalar-tensor theory of the core collapse events. We identify a remarkably simple and straightforward classification scheme of the resulting collapse events. For any given set of parameters, the collapse leads to one of three end states, a weakly scalarized neutron star, a strongly scalarized neutron star or a black hole, possibly formed in multiple stages. The latter two end states can lead to strong gravitational-wave signals that may be detectable in present continuous-wave searches with ground-based detectors. We identify a very sharp boundary in the parameter space that separates events with strong gravitational-wave emission from those with negligible radiation.