Gravitational radiation from compact binary systems in the massive Brans-Dicke theory of gravity

We derive the equations of motion, the periastron shift, and the gravitational radiation damping for quasicircular compact binaries in a massive variant of the Brans-Dicke theory of gravity. We also study the Shapiro time delay and the Nordtvedt effect in this theory. By comparing with recent observational data, we put bounds on the two parameters of the theory: the Brans-Dicke coupling parameter omega BD and the scalar mass m(s). We find that the most stringent bounds come from Cassini measurements of the Shapiro time delay in the Solar System that yield a lower bound omega(BD) > 40 000 for scalar masses m(s) < 2.5 X 10(-20) eV [or Compton wavelengths lambda(s) = h/(m(s)c) > 5 X 10(10) km], to 95% confidence. In comparison, observations of the Nordtvedt effect using lunar laser ranging experiments yield omega(BD) > 1000 for m(s) < 2.5 X 10(-20) eV. Observations of the orbital period derivative of the quasicircular white dwarfneutron star binary PSR J1012 + 5307 yield omega(BD) > 1250 for m(s) < 10(-20) eV (lambda(s) > 1.2 X 10(11) km). A first estimate suggests that bounds comparable to the Shapiro time delay may come from observations of radiation damping in the eccentric white dwarf-neutron star binary PSR J1141 - 6545, but a quantitative prediction requires the extension of our work to eccentric orbits.