Radiation reaction force for scalar-tensor theories in effective-one-body formalism

While most of the binary configurations in modified theories of gravity are studied under quasicircular orbit limit, eccentricity effects could play a significant role in future gravitational wave detections. We derive the gravitational radiation reaction force for nonspinning eccentric orbits within the effective-one-body (EOB) description for the massless scalar-tensor theories up to 1.5 post-Newtonian (PN) order. The effects in such theories start at <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mn>1</a:mn> <a:mo>/</a:mo> <a:msup> <a:mi>c</a:mi> <a:mn>3</a:mn> </a:msup> </a:math> and interestingly, the 1.5PN order effect is due to radiation reaction square effects, which is a conservative effect. The results derived here can be implemented in the quasicircular EOB-based waveform models to construct waveform templates for generic orbit binaries within massless scalar-tensor theories of gravity.