Constraining self-interactions of a massive scalar field using scalar gravitational waves from stellar core collapse

We perform a comprehensive numerical study of gravitational waves from stellar core collapse in the massive scalar-tensor theory with the cubic and quartic self-interactions of the scalar field. We investigate the dependence of gravitational waves on the self-interaction as well as the mass of the scalar field and the conformal factor. We find that gravitational-wave spectra show a systematic difference between the cubic and quartic self-interactions. We also find that this systematic difference is insensitive to the mass of the scalar field and the conformal factor. Our results indicate that the type of the self-interaction could be constrained by observations of gravitational waves using the future-planned detectors.