Test of the Brans–Dicke theory with GW200105 and GW200115

Abstract

Abstract We study whether it is possible to constrain the Brans–Dicke (BD) theory from the measurement of gravitational waves (GW) released in neutron star-black hole collisions. Considering the scalar field modifications through monopole and dipole radiations, we find additional contributions to the phase evolution in the emitted gravitational waveform. After effectively calculating such effect in the post-Newtonian order, we are in a position to measure the scalar field and give bounds on the BD coupling parameter ω BD . We derive the analytical expression for the phase modification due to the orbital eccentricity of eccentric binaries in both general relativity and BD theory. Employing the Bayesian analysis, we obtain the constraints on ω BD from the GW events, GW200105 and GW200115.