Dynamics of compact binary systems in scalar-tensor theories. II. Center-of-mass and conserved quantities to 3PN order

The equations of motion of nonspinning compact binary systems at the third post-Newtonian (PN) order in massless scalar-tensor theories have recently been obtained. In the present paper, we complete this work by computing at 3PN order the ten integrals of motion together with the equations of motion in the center-of-mass frame. We then perform the reduction of the center-of-mass equations to quasicircular orbits and determine the conserved energy and angular momentum for circular orbits.