# Inverse-chirp signals and spontaneous scalarisation with self-interacting potentials in stellar collapse

## TL;DR

This paper investigates how scalar self-interactions affect gravitational wave signals from stellar collapse in scalar-tensor gravity, finding that inverse-chirp signals are robust unless self-interaction terms are significantly amplified.

## Contribution

It introduces a detailed analysis of scalar self-interactions' effects on gravitational wave signals during stellar collapse, extending previous models with higher-order potentials.

## Key findings

- Inverse-chirp signals are robust against higher-order potential modifications.
- Significant differences in wave signals occur only with amplified self-interaction terms.
- Robustness persists unless self-interaction parameters are fine-tuned by over five orders of magnitude.

## Abstract

We study how the gravitational wave signal from stellar collapse in scalar-tensor gravity varies under the influence of scalar self-interaction. To this end, we extract the gravitational radiation from numerical simulations of stellar collapse for a range of potentials with higher-order terms in addition to the quadratic mass term. Our study includes collapse to neutron stars and black holes and we find the strong inverse-chirp signals obtained for the purely quadratic potential to be exceptionally robust under changes in the potential at higher orders; quartic and sextic terms in the potential lead to noticeable differences in the wave signal only if their contribution is amplified, implying a relative fine-tuning to within 5 or more orders of magnitude between the mass and self-interaction parameters.