Gravitational Dipole and Quadrupole Radiation from Pulsars

I shall present the theoretical background for the data analysis of gravitational waves (GWs) from spinning neutron stars in Brans-Dicke (BD) theory. Einstein’s general theory of relativity (GR) predicts only two tensor polarization states but a generic metric theory of gravity can also possess scalar and vector polarization states. The BD theory attempts to modify the GR by varying gravitational constant G, and it has three polarization states. The first two states are the same as in GR, and the third one is the scalar polarization. We derive the response of a laser interferometric detector to the GW signal from a spinning neutron star in BD theory. We obtain a new statistic (D-statistic) based on the maximum likelihood principle to identify the signal in BD theory in the detector’s noise. This statistic generalizes the well known F-statistic used in the case of GR. We perform Monte Carlo simulations in Gaussian noise to test the detectability of the signal and the accuracy of estimation of its parameters. We implemented our codes in the LIGO-Virgo-KAGRA pipeline to search for the dipole radiation in BD theory.